As the little marks added between words, punctuation is like a system of traffic signs: it guides the reader towards the intended meaning of the words just as road signs guide drivers to their destination. They tell the reader when to go, when to pause, when to stop, when to go again, when to pay close attention, and when to turn (Truss, 2003, p. 7). They’re also crucial for avoiding accidents. A paragraph without punctuation—no periods, commas, apostrophes, etc.—quickly spins out into utter nonsense and kills the reader’s understanding of the writer’s meaning.

Punctuation that’s merely missing or unnecessary here and there can confuse a reader and even lead to expensive lawsuits if they plague contentious documents like contracts. To anyone who knows how to use them, seeing punctuation mistakes in someone else’s writing makes that other person look sloppy and amateurish. Punctuation errors by adult native English speakers look especially bad because they reflect poorly on their education and attention to detail, especially if they’re habitual mistakes. The critical reader looks down on anyone who hasn’t figured out how to use their own language in their 20+ years of immersion in it. Not knowing the difference between a colon and semicolon, for instance, is like not knowing the difference between a cucumber and a zucchini; sure they look alike from a distance, but they’re completely different species and serve different culinary functions. If you don’t know these differences by the time you’re an adult, however, it doesn’t take much to learn.

In this section, we focus on how to spot and correct common punctuation errors, starting with commas because most problems with people’s writing in general are related to missing and misused commas. The goal is to help you avoid making mistakes that can potentially embarrass you in the eyes of people who should be taking you seriously.

D.3.1: Commas

Most punctuation problems are comma-related because of the important role commas play in providing readers with guidance on how a sentence is organized and is to be read to understand the writer’s intended meaning. Commas signal to the reader where one clause ends and another begins in compound and complex sentences, but they serve several other roles as well. We use commas in four general ways, each with several variations and special cases. To these we can add rules about where not to add commas, since many writers confuse their readers by putting commas where they shouldn’t go. Most style guides advocate for using as few commas as possible, though you certainly must use them wherever needed to avoid ambiguities that lead readers astray. Closely follow the sixteen rules below to guide your reader towards your intended meaning and avoid confusing them with comma misplacement.

Quick Rules: Commas

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common comma errors associated with each one.

Extended Explanations

Comma Rule 1.1: Put a comma before coordinating conjunctions in compound sentences.

Put a comma before the coordinating conjunction (e.g., and, but, so; Darling, 2014a) that joins two independent clauses in a compound sentence. A compound sentence contains two or more clauses that can stand on their own as sentences with a different subject in each clause.

How This Helps the Reader

The comma tells the reader to pause a little after one independent clause ends and before the coordinating conjunction signals that another (with a new subject) is joining it to make a compound sentence. In each of the examples sentences above, the independent clause on either side of the comma-conjunction combination could stand on its own as a sentence. In the first example above, for instance, we could replace the comma and conjunction with a period, then capitalize the o in “our,” and both would be grammatically correct sentences. We combine them with a comma and the conjunction and, however, to clarify the relationship between the two ideas. The comma signals that these are coordinated clauses rather than noun or verb phrases.

If the subject were the same in both clauses, however, both the comma and subject of the second clause would be unnecessary. In that case, the sentence would just be a one-subject clause with a compound predicate—that is, two coordinated verbs (see Comma Rule 4.4 below). Consider the following examples:

What to Look for When Proofreading

Look for run-on sentences (see §D.2.1.2), which are sentences that omit a comma before the coordinating conjunction joining two independent clauses. Keep an eye out for the seven coordinating conjunctions for, and, nor, but, or, yet, and so (use the mnemonic acronym fanboys to remember them). Simply add a comma before the conjunction if the independent clause on either side of the conjunction could stand on its own as a sentence because it has a subject and predicate.

In the example above, the coordinating conjunction “but” joins the two independent clauses beginning with the subjects “We” and “Our long-term plan.” Omitting the comma in the first example makes the sentence a run-on. Misplacing the comma after the conjunction in the second miscues the reader to pause after, rather than before, the conjunction. The easy fix is just to add the comma or move it so it goes before the conjunction.

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Comma Rule 1.2: Don’t put a comma between independent clauses in a compound sentence if not followed by a coordinating conjunction.

Don’t put a comma between two independent clauses if it’s not followed by a coordinating conjunction because this is a comma splice sentence error (see §D.2.1.2). We have two distinct ways of forming a compound sentence and a comma splice confuses the two. One way of making a compound sentence is to join independent clauses by placing a comma and one of the seven “fanboys” coordinating conjunctions between them. Simply omitting the coordinating conjunction after the comma makes a comma splice. The other way of making a compound sentence is to end the first clause with a semicolon when it doesn’t make sense to use any of the coordinating conjunctions to establish a certain relationship between the clauses (see Semicolon Rule 1 below). Using a comma instead of a semicolon in such compound sentences makes a comma splice.

What to Look for When Proofreading

Look for commas separating two independent clauses (clauses that can stand on their own as sentences because they each have a subject and predicate) without any of the seven coordinating conjunctions (for, and, nor, but, or, yet, or so) following the comma.

In the incorrect example above, the comma separates two independent clauses that can stand on their own as sentences if you replaced the comma with a period and capitalized the t in “the second.” You have three options for fixing the comma splice corresponding to the three examples above:

1. Replace the comma with a semicolon to make a compound sentence.
2. Add a coordinating conjunction, such as but, to make a compound sentence that clarifies the relationship between the clauses.
3. Add a subordinating conjunction, such as Though, at the beginning of the first clause to make it a dependent (a.k.a. a subordinate) clause. This makes the sentence a complex one.

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Comma Rule 2.1: Put a comma after introductory subordinate clauses, phrases, or words preceding main clauses.

Put a comma before the main clause (a.k.a. independent clause) when it is preceded by an introductory word, phrase (e.g., a prepositional or participial phrase), or subordinate clause (a.k.a. dependent clause) in a complex sentence.

How This Helps the Reader

The comma tells the reader to pause a little prior to the main clause as if to say, “Okay, here’s where the sentence really begins with the main-clause subject and predicate.” The main clause is the main point, whereas the subordinate clause that precedes it is relatively minor, providing context.

Recall that a complex sentence is one where a subordinating conjunction begins an independent or subordinate clause, which cannot stand on its own as a sentence. A subordinate clause (a.k.a. dependent clause) becomes part of a proper sentence only when it joins a main (a.k.a. independent) clause. When that subordinate clause precedes the main clause, a comma separates them. The same is true when that main clause is preceded by a phrase (e.g., prepositional, infinitive, participial, gerund, etc.; Darling, 2014b) or even just a word such as an appositive participle (as in the “Delighted” example above) or conjunctive adverb (Darling, 2014c), as in the “Therefore” example above.

What to Look for When Proofreading

Look for words, phrases, or clauses preceding the main clause without a comma separating them. For this, you must know how to spot the main clause when it comes later in the sentence; in other words, you need to be able to spot the main grammatical subject (the doer of the action) and predicate (the action itself). If the main subject is preceded by words, phrases, or clauses but not a comma, then you need to add one before the main clause.

In the example above, “you” is the main grammatical subject that begins the main clause, whose main verb is “come.” The subordinate clause begins with the subordinating conjunction “Because” and ends at “ones,” so the comma must follow “ones” to separate it from the beginning of the main clause.

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Comma Rule 2.2: Don’t put a comma after main clauses followed by subordinate clauses or phrases unless the latter strikes a contrast with the former.

Don’t put a comma after a main clause (a.k.a. independent clause) if it is followed by a subordinate (a.k.a. dependent) clause or phrase in a complex sentence. If the subordinate clause begins with a contrasting subordinating conjunction such as “although,” a comma must separate the two clauses.

How This Helps the Reader

The absence of the comma tells the reader to keep reading smoothly without pause between the main and subordinate clauses. In the case of the contrasting subordinate clause, however, the comma signals a pause as if to say that the subordinate clause is a kind of afterthought or qualification added to the main clause.

What to Look for When Proofreading

Look for commas unnecessarily added before subordinating conjunctions in complex sentences where the subordinate clause follows the main clause and doesn’t strike a contrast with it.

In the examples above, the comma is simply unnecessary and should be deleted. It would be necessary, however, if the first sentence began with the subordinate clause beginning with “Because . . . ” or after the infinitive phrase if the second sentence began with “To create . . . .” In those cases, the comma would follow “gasket” and “2003” respectively and you would change the first letter in the main clauses to lowercase.

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Comma Rule 3.1: Put commas around parenthetical words, phrases, or clauses.

Put commas before and after parenthetical or non-essential words, phrases, or clauses that would leave the sentence grammatically correct if you omitted them. Placed in the middle of a sentence between the subject and predicate or at the end of the sentence, however, those elements lend further detail to the words or phrases that come just before them. Commas in this way function as a lighter form of parentheses (see §5.3.5 below).

How This Helps the Reader

As light alternatives to parentheses, these parenthetical commas tell the reader to pause a little when a non-essential (a.k.a. parenthetical) point is interjected or tacked on to explain the word or phrase preceding it. Common parenthetical phrases include:

Interestingly, this rule also helped the Atlantic Canada telephone company Bell Aliant cancel a contract with Rogers Communications over the use of telephone poles prior to Rogers’s intended five-year term, costing Rogers a million dollars and resulting in a bitter court battle in 2006. The dispute concerned the following sentence in the middle of the 14-page contract:

This agreement shall be effective from the date it is made and shall continue in force for a period of five (5) years from the date it is made, and thereafter for successive five (5) year terms, unless and until terminated by one year prior notice in writing by either party.

Without the comma after “terms,” you could read the contract as Rogers intended, which was to say that it could be terminated with a year’s notice any time after the first five years. By adding the second comma to make the “and thereafter” phrase parenthetical and therefore non-essential, however, Rogers in effect made the “unless . . .” clause apply to the first five-year term as well as to any subsequent term. That one misplaced comma thus gave Bell Aliant the right to cancel at any time.

Citing this parenthetical comma rule, the Canadian Radio-Telecommunications Commission (CRTC) ruled in favour of Bell Aliant at Rogers’s expense (Austen, 2006). The CRTC later reversed its ruling when Rogers invoked the less ambiguous French version of the contract to force Aliant to return to its contractual obligations. Still, Rogers ultimately paid heavily for un-recouped losses during the contract’s cancellation and in legal fees throughout the contract dispute, which dragged out till 2009 (Bowal & Layton, 2014). You can bet Rogers pays people to ensure its contracts are punctuated unambiguously now.

What to Look for When Proofreading

Look for words, phrases, or clauses that could be deleted from a sentence without making it grammatically incomplete. Add commas if none mark off the parenthetical word, phrase, or clause, or if the first is there but not the second (or vice versa) in the case of parenthetical elements ending a sentence.

Here, the non-essential parenthetical relative clause beginning with the non-restrictive relative pronoun which and ending with “word,” could be deleted from the sentence and leave it grammatically complete. However, as an interjection, it clarifies the word that precedes it (“gesticulation”), and therefore has a place in the sentence, albeit one set apart from the rest.

Here, the comma is crucial in signalling that Grandpa is being addressed. Without the comma, the sentence recommends preparing Grandpa to be cooked and presumably eaten, which is hopefully not the intended meaning.

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Comma Rule 3.2: Put a comma before contrasting coordinate elements, end-of-sentence shifts, and omitted repetitions.

Put commas before end-of-sentence:

• Questions that seek confirmation of the main-clause point by asking the opposite
• Phrases that begin with not and state what the main-clause point seeks to correct
• Coordinate elements that contrast or further extend the main-clause point

What to Look for When Proofreading

Look for run-on-like gaps where no punctuation separates the main clause from questions or contrasting phrases tacked on to the end of a sentence, and add the comma.

Here, the main clause ends with “alive,” and the follow-up recasting of the statement as an interrogative sentence (“isn’t this the best time to be alive?”) abbreviated as “isn’t it?” forms a run-on without any punctuation separating it from the main clause. The comma added between the clauses represents the words that were omitted to avoid repetition.

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Comma Rule 3.3: Put a comma before sentence-ending free-modifier phrases that describe elements at the beginning or middle of sentences.

Put commas before phrases that appear at the end of a sentence but modify (describe) actions or things at the sentence’s beginning or middle. As long as such phrases don’t cause confusion with their ambiguity, they are free to either follow the noun they modify or appear at the end.

How This Helps the Reader

The comma signals to the reader that the phrase ending the sentence refers to something that came earlier in the sentence. Without a comma, the phrase would describe what came immediately before it.

What to Look for When Proofreading

Look for phrases (especially participial phrases—words ending -ing) at the end of sentences without commas preceding them but not making sense. If they indeed have commas preceding them but the participle could refer to more than one thing in the main clause, resolve the ambiguity by moving the phrase closer to the thing it modifies.

Here, the omitted comma makes it seem like the gratuity is smiling obsequiously, which doesn’t make sense. Adding the comma before “smiling” makes it clear that the bellhop mentioned earlier in the sentence is the one smiling.

The participial phrase is ambiguous when placed at the end of the sentence because it’s unclear whether the MC or plenary speaker is bowing graciously. Moving the participial phrase to the beginning so that it is in appositive relation to the noun it modifies clarifies the sentence to say that the MC is bowing.

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Comma Rule 3.4: Put commas around higher levels of organization in dates, places, addresses, names, and numbers.

Put commas around the:

• Year when preceded by a month and date
• Date when preceded by a day of the week
• Larger geographical region (e.g., province, state, country, etc.) when preceded by smaller one (e.g., city or town) in a sentence or long address line
• Title or credential (e.g., ND, MD, PhD) following a name
• Groups of thousands in large numbers

How This Helps the Reader

The commas tell the reader to pause a little within a detailed series of time, geographical, or name designations when adding a higher order of organization just as commas were used as light alternatives to parentheses in Comma Rule 3.1.

What to Look for When Proofreading

Look for years added to three-part dates, larger geographical regions added after cities and towns, or credentials added after names with either no comma added on either side of that year, region, or credential, or added only before it but not after. Add both or the second comma. If the date only has the month and year, but a comma or two surrounds the date, delete commas.

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Comma Rule 3.5: Put a comma between a signal phrase and a quotation.

Put commas between signal phrases and the quotations they introduce when the signal phrases end with a verb that gives rise to the quoted words or thoughts.

How This Helps the Reader

The comma cues the reader to pause as it abbreviates the relative pronoun that, which makes the comma unnecessary if it’s included.

What to Look for When Proofreading

Look for missing commas around quotations and add them between the signal phrase ending with a verb and the quotation, or look for unnecessary commas that split a sentence unnaturally, such as going before or after the that that precedes a quotation if present), and delete them.

Here, a comma unnecessarily follows the relative pronoun that perhaps because the writer thought that a comma should always precede the quotation. You could either delete the comma or “that,” but not both.

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Comma Rule 3.6: Don’t put commas around restrictive relative clauses (before that).

Don’t put a comma before a restrictive relative clause (e.g., beginning with the relative pronoun who or that) following a main clause.

How This Helps the Reader

The absence of the comma tells the reader that the relative clause starting with the relative pronoun that or who is essential to the meaning of the sentence and should be read smoothly without pauses around it. For more on restrictive and non-restrictive relative clauses, see Introduction and General Usage in Defining Clauses (Keck & Angeli, 2018) .

What to Look for When Proofreading

Look for commas preceding that or who and determine whether the meaning of the sentence would be significantly changed if you deleted the restrictive relative clause. If it would be, delete the commas.

Here, the restrictive relative clause beginning with that is essential to the meaning because it clarifies what kind of facts are common knowledge. It is not interchangeable with the non-restrictive relative clause beginning with which, which requires a comma before it because it is non-essential (see Comma Rule 3.1 above). In the UK, writers often use “which” instead of “that” even in non-restrictive relative clauses without the comma preceding them. In North America, however, we distinguish the relative clause types by using a comma and which for non-restrictive clauses and that without a comma for restrictive clauses.

Here, the commas in the incorrect sentence say that all students were caught plagiarizing. Deleting the commas to make “who were caught plagiarizing” a restrictive relative clause brings the sentence back to the intended meaning, which is that a subset of students were caught plagiarizing and the rest did well.

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Comma Rule 3.7: Don’t put commas between subjects and their predicates.

Don’t put a comma between a clause’s subject (even if it’s a long one) and predicate (the main verb action) if there are no parenthetical elements between them.

How This Helps the Reader

The absence of the comma tells the reader to read smoothly across the subject and predicate because they are the integral parts of a unified clause even if the subject is long.

What to Look for When Proofreading

Look for commas that separate the subject from the predicate when there are no parenthetical words or phrases, or non-restrictive clauses, separating them. For this, you must know how to spot the main-clause subject and predicate and delete any stray commas that come between them.

The subject of the above sentence is a long one because, following the core noun “businesses,” it contains a restrictive relative clause beginning with that, which contains prepositional phrases (“from the new . . .” and “of Bill 134”) and a participial phrase (“following . . .”). None of these length-extending units change the fact that there is no legitimate parenthetical interjection requiring commas between the subject and the predicate that begins with “have given.” The easy fix is just to delete the comma.

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Comma Rule 4.1: Put commas between each item in a series, including the last two items.

Put commas between each item in a series, including before the and or or that separates the second-to-last (a.k.a. penultimate) and last items, whether those items be words, phrases, or even clauses in a series.

How This Helps the Reader

The serial commas help separate each item in the series, and the one that comes before the coordinating conjunction and that joins the last two items (a.k.a. the “Oxford comma”), helps resolve various ambiguities that may arise without it (see some below). The question of whether to use the Oxford comma has been a long-running debate. Some style guides, such as the Canadian Press, Associated Press, and even institutions like Algonquin College, recommend omitting it because they advocate for as few commas as possible. However, they say nothing about situations where omitting the Oxford comma creates unavoidable ambiguity—that is, two interpretations that mean two very different things. The anti-Oxford comma side even has an anthem in the Grammy-winning indie band Vampire Weekend’s 2008 debut-album single “Oxford Comma,” which opens with the lyric “Who gives a f**k about the Oxford comma?”.

Direct link: https://youtu.be/P_i1xk07o4g

However, grammarians, readers, and writers who care about clarity in writing, and even the plaintiffs awarded $5 million in a US civil suit (as well as the defendants paying the price) certainly care about the Oxford comma. The significant confusion and even conflict that results from its absence in clutch situations justifies its inclusion in all. For instance:

• In a 2017-2018 civil case that went nearly as far as the US Supreme Court, Oakhurst Dairy of Portland, Maine, was ordered to pay its delivery drivers $5 million due to the ambiguity caused by an omitted Oxford comma in state law. The law was soon amended to separate the last two items in a list of overtime pay exemptions to resolve the ambiguity (Victor, 2018).
• The inclusion or omission of the Oxford comma leads to two entirely different interpretations when names are listed. If you were to say, for instance, that you and two others must go to court, you would say, “Beth, Ian, and I must go to court.” Without the Oxford comma, however, you would be addressing Beth (who now isn’t going to court) to tell her that just you and Ian are going: “Beth, Ian and I must go to court,” which is not what you originally meant.
• Appositive relations between items in a series also create ambiguities when omitting the Oxford comma. If an actor winning a big award in front of a national audience were to say, “I would like to thank my parents, God and Buffy Sainte-Marie,” the absence of an Oxford comma makes “God and Buffy Sainte-Marie” appear to be an appositive noun phrase modifying “parents”—that is, she would imply that her parents are God and Buffy Sainte-Marie. By using the Oxford comma, she avoids this absurdity by thanking three entities: her parents, God, and Buffy Sainte-Marie—as intended.
• Omitting the Oxford comma is especially confusing if the items listed are a combination of paired and single items. If the list of pairs in the fourth correct example above omitted the Oxford comma, it would end with the absurdity of having the last four items appearing as singles with “and” awkwardly separating each: “. . . Steven Tyler and Joe Perry, Axl Rose and Slash and Anthony Kiedis and John Frusciante.” Knowing the context of these pairings would help resolve the ambiguity, but if you were reading a list of unknown mixed single and paired items, you wouldn’t know which was a single and which was a pair near the end without the Oxford comma. A list such as “A, B and C, D, E and F, G, H, I, J and K and L” would be ambiguous because you wouldn’t know if the last three items paired J with K (and L is single) or K with L (and J is single).

If the Oxford comma is necessary to avoid ambiguity in such cases, it should be used as a rule in all cases. Writers shouldn’t have to make a subjective judgment call about whether the reader would find it ambiguous with or without the Oxford comma because some readers are more astute than others. Except perhaps in titles where brevity is highly valued and no ambiguities of the kind listed above can confuse the reader, the Oxford comma should always be used.

What to Look for When Proofreading

Look for list of three or more words, phrases, or clauses in a sentence. If you don’t see a comma before the and that separates the last two items, add one there.

Omitting the Oxford comma in the incorrect example above suggests that you and your friend are non-contributors because “my friend and me” are in appositive relation to “non-contributors.” Though you did not mean to say this, you are in effect offering yourself and your friend as particular examples of non-contributors. By adding the Oxford comma, however, you now say that the group is comprised of you, your friend, and some non-contributors. With the Oxford comma, you and your friend are productive members rather than non-contributors despite being grouped with them.

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Comma Rule 4.2: Put commas between two or more coordinate adjectives.

Put commas between two or more coordinate adjectives that refer to the same noun. Coordinate adjectives are those stacked in front of a noun in no particular order to describe the noun in multiple ways. You can tell that they’re coordinate adjectives if you can (1) change their order and (2) add and between each without changing the meaning either way.

How This Helps the Reader

The commas distinguish coordinate from non-coordinate adjectives, and therefore what adjectives are incidental and which are intrinsic qualities of the noun they describe. For more, see Commas and Coordinate Adjectives (Grammar Revolution, 2020) and Comma Tip 6: Use Commas Correctly with a Series of Adjectives (Simmons, 2018a).

What to Look for When Proofreading

Look for a series of two or more adjectives preceding a noun without commas between them. If you can put and between them and change their order without changing the meaning of the sentence, they’re coordinate adjectives that need commas between them.

The only adjectives that could be swapped around and have and added between them are “vicious” and “unrelenting.” The adjective “freezing” is locked in its position before the noun “rain” to mean the type of rain that makes the outside one huge ice rink. Therefore, you need to add a comma between “vicious” and “unrelenting,” but not between “unrelenting” and “freezing.”

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Comma Rule 4.3: Don’t put a comma after the final coordinate adjective.

Don’t put a comma after the second of two (or third of three, etc.) coordinate adjectives—i.e., between the final coordinate adjective and the noun it describes. See Comma Rule 4.2 above for a further explanation of coordinate vs. non-coordinate adjectives.

What to Look for When Proofreading

Look for coordinate adjectives preceding a noun with commas between them. If you can put and between them and change their order without changing the meaning of the sentence, they’re coordinate adjectives that need commas between them.

The only adjectives that could be swapped around and have and added between them are “common” and “basic.” In this case, “information technology” (a.k.a. “IT”) is a noun phrase that modifies the noun “tools,” so their order is locked in, making them non-coordinate.

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Comma Rule 4.4: Don’t put a comma between non-coordinate adjectives.

Don’t put commas between non-coordinate adjectives—that is, between adjectives that are in a fixed order before the noun they modify and cannot have and added between them without changing the meaning of the sentence. See Comma Rule 4.2 above for a further explanation of coordinate vs. non-coordinate adjectives.

What to Look for When Proofreading

Look for coordinate adjectives preceding a noun with commas between them. If you can’t put and between them and change their order without changing the meaning of the sentence, they’re non-coordinate adjectives. Any commas between them must be deleted.

The order is important in the first set of non-coordinate adjectives describing the noun “kit” because the type of kit we’re dealing with is a drum kit, so “drum” must come immediately before “kit.” The brand of drum kit is Pearl (capitalized because it is a proper noun), so “Pearl” precedes “drum kit.” The only adjective preceding these non-coordinate adjectives is “black,” but it is unaccompanied by another to make it a coordinate adjective, so there are no commas. Likewise, inserting a comma between “heavy” and “metal” splits the musical genre “heavy metal” serving as a non-coordinate adjective to “drummer,” so it misleadingly implies that the drummer is a 400kg led statue.

Comma Rule 4.5: Don’t put commas between two coordinate nouns or verbs.

Don’t put commas between two nouns (or noun phrases) or verbs (or verb phrases) joined by the coordinating conjunction and in a compound subject, predicate, or object.

What to Look for When Proofreading

Look for commas appearing before or after the coordinating conjunction and when it comes between nouns (or noun phrases) or verbs (or verb phrases), then delete them.

This above sentence features a compound subject, meaning that two subjects (the two communications directors) perform the main action (“met”). Though each is followed by a prepositional phrase (“from . . .”), the comma between them must be deleted in the incorrect sentence to avoid impeding the reader.

The sentence above has a compound predicate, meaning that the one subject (“They”) performed two actions (“applied” and “worked”). Again, the comma is unnecessary between them and must be deleted from the incorrect sentence. The comma would be necessary if the second verb had a different subject performing the action, in which case they would be two independent clauses in a compound sentence (see Comma Rule 1.1).

The above sentence also has a compound predicate (“can’t expect” and “not pay”). Adding a comma makes this out to be a compound sentence, which it isn’t because the subject “They” is common to both actions. To avoid an “X and Y and Z” structure caused by having a compound object (“report and memo”) appearing just before the conjunction coordinating the second verb, the “and” joining the two verb phrases can simply be changed to “but.”

The above sentences have a compound object, meaning that two objects (“deadline” and “timeline”) are acted upon by the verb “gave.” The objects here are in somewhat long noun phrases, but to add a comma between them (after ”schedule”) would mislead the reader into thinking that this is a compound sentence with a new independent clause following “and.” Deleting the comma would ensure that the reader understands the sentence instead as a simple sentence with a compound object.

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For more on commas, see the following resources:

• Purdue OWL’s Extended Rules for Using Commas (Driscoll & Brizee, 2018) along with its Punctuation Exercises: Commas (Purdue OWL, 2010).
• The Punctuation Guide’s Comma page (Penn, 2011a)
• The Grammar Book’s Commas page and its Commas Quiz 1 and Commas Quiz 2 (Straus, 2018a)

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D.3.2: Apostrophes

Apostrophes are mainly used to indicate possession and contraction but are probably the most misplaced punctuation mark after commas. They can embarrass the writer who misuses them, show a lack of attention to detail, and confuse readers about whether a noun is singular or plural, possessive, a contraction, or just a misspelling. Used properly, apostrophes at the end of a noun cue readers that the noun following is possessed by what the noun preceding refers to. For instance, in “Uncle Tom’s cabin,” the apostrophe indicates that the cabin (noun) is owned by Uncle Tom. Placement of apostrophes before or after the s ending a word determines if the noun is plural or singular. They’re also used for contractions in informal writing such as you see at the beginning of this sentence. You have four main rules to follow when using apostrophes, as well as several special cases.

Quick Rules: Apostrophes

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common apostrophe errors associated with each one.

Extended Explanations

Apostrophe Rule 1.1: Put an apostrophe before the s ending a singular possessive noun.

Put an apostrophe before the s added to the end of a singular noun when the noun or noun phrase following belongs to the noun preceding it. In the case of joint ownership in compound nouns (when two or more nouns have joint possession of the noun following), the apostrophe-s goes only at the end of the second or final noun.

How This Helps the Reader

The apostrophe before the s signals to the reader that the preceding singular noun is in possession of the noun or noun phrase following. To test whether you are dealing with a case of possession, you can flip the order and insert “of the” between the nouns or noun phrases. In the first example above where the brain belongs to Einstein, for instance, “the brain of Einstein” is a wordier equivalent of “Einstein’s brain” but confirms possession.

What to Look for When Proofreading

Look for s added to the end of words when your intention is to show possession, but you’ve omitted the apostrophe, making the word look like a simple plural. Add the apostrophe. Also, in cases where an apostrophe is added to the very end of a singular noun that ends in s to show possession (see the second correct example above), add another s rather than imply that the singular noun is plural.

The incorrect sentence above contains three apostrophe errors:

• The company belongs to Mr. Davis, who is just one person and is therefore grammatically singular despite having a name ending in s. Perhaps the writer heard that you can’t have an “s’s” due to pronunciation concerns, but usually we pronounce this Day-viss-ez to indicate possession. Thrown by this and confusing the singular and plural possessive forms, the writer who omits the s and may cause the same confusion can avoid doing so by adding it.
• The proposal belongs to the company, but the apostrophe is omitted and the plural form of company (“companies”) is given instead of “company’s.” The error is likely due to the fact that the plural noun and singular possessive noun forms are homophones—they sound exactly alike but are spelled differently and mean different things (see homophone.com for several examples of such homophones). Correcting this is a simple matter of replacing “ies” with “y’s” at the end of the word.
• Finally, the request is in the proposal and thus belongs to it. Omitting the apostrophe makes the plural noun “proposals,” and fixing it is just a matter of adding the apostrophe before the final s.

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Apostrophe Rule 2.1: Put an apostrophe after the sending a plural possessive noun.

Put an apostrophe after the s at the end of a plural noun (a noun of two or more people, places, or things) when the noun or noun phrase following belongs to it.

How This Helps the Reader

The apostrophe after the s tells the reader to read the noun as being a plural in possession of the noun or noun phrase following, as opposed to the apostrophe before the s signalling a singular possessive.

What to Look for When Proofreading

Look for plural words that end in s being in possession of the noun following without an apostrophe at the end, or the apostrophe added before the s. Either add the apostrophe to the end of the word or move the it there.

Here, the grace period belongs to the two months (plural), so omitting the apostrophe is incorrect because it leaves “months” as a simple plural. The apostrophe-s ending is also incorrect because it makes “month” singular, which disagrees with the “two” preceding. To correct these errors, the apostrophe must go after the s at the end of “months.”

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Apostrophe Rule 2.2: Don’t put an apostrophe before the s ending a non-possessive plural decade

Don’t put an apostrophe between the 0 and s when writing a plural decade that’s not possessive (e.g., 1990s). Put an apostrophe at the end only if the decade is in possession of the noun or noun phrase following.

How This Helps the Reader:

The apostrophe after the s signals to the reader that the noun or noun phrase following happened in the decade given. Some mistakenly put an apostrophe between the 0 and s when referring to the simple plural of a decade (e.g., 1990’s), but this conflicts with the singular possessive form of the year (see the “1980’s” example above). If the decade were also possessive, “1990’s’” (with two apostrophes—one before and one after the s) would look awkward. The non-possessive apostrophe between the 0 and s is probably confusing the rule that places the contraction apostrophe before the last two digits of the year or decade (see the third example in Apostrophe Rule 3 below).

What to Look for When Proofreading

Look for an apostrophe-s added to the end of a decade and delete the apostrophe if the decade (or year at the beginning of the decade) isn’t in possession of the following noun or noun phrase.

In the incorrect sentence above, “1990’s” is the singular possessive form of “1990,” meaning something belonging to the year 1990 should follow it rather than a verb. Perhaps the writer confused “1990’s” with the contraction “ ’90s.” The apostrophe before the s must be deleted to make the simple plural “1990s,” meaning all the years from 1991 to 2000 inclusive.

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Apostrophe Rule 3: Put an apostrophe where letters are omitted in contractions.

Put an apostrophe wherever letters and characters (including spaces) have been omitted in contractions. Contractions are two (sometimes more) words combined into one word to represent the way they’re often said quickly as one word in informal speech. In the examples below, the contractions would be incorrect if formal writing were expected by the audience but are correct as informal writing.

How This Helps the Reader

The apostrophe replaces omitted letters in contractions and thus signals informal writing meant to represent the way we speak words informally, though they would be unacceptable in formal writing. Some common contractions that often confuse readers because they are homophones with other words include:

Table 5.3.2: Commonly Confused or Misspelled Contractions

For a more exhaustive set, see the List of English contractions (Wikipedia, 2021).

What to Look for When Proofreading

Look for the absence of apostrophes in contractions and add them. Your spellchecker will help catch these in most cases (see Table 5.1.4.8 ), but you must be especially careful in seeking them out if your spellchecker has any difficulty. Ensure also that you always use the form of apostrophe that looks like a small superscript “9,” not “6” (the opening of single quotation marks; see Quotation Marks Rule 2) especially when placed at the beginning of words or numbers.

The many errors in the incorrect sentence can be corrected in the following ways:

• It’s (for “it is”) is meant rather than the third-person possessive pronoun Its
• they’re (for “they are”) is meant rather than the pronoun there
• gonna (for “going to”) is meant rather than “gone to,”
• I’m (for “I am”) is meant rather than “im”
• you’re is meant rather than the possessive pronoun “your”

The errors in the incorrect sentence can be corrected in the following ways:

• can’t (for “cannot”) is meant rather than cant, meaning “slang.”
• ’70s (for 1970s with the apostrophe like a superscript “9”) is meant rather than the opening single-quotation mark (like a superscript “6”); the trick to getting the correct direction of apostrophe is to type any letter first, then the apostrophe to orient it in the form appearing as a small superscript “9,” and then go back to delete the letter in front of it
• n’ (for “and”) is meant rather than the opening single-quotation mark (like a superscript “6”) appearing before the n; an apostrophe replacing the a, in addition to the one for d, is seen as excessive

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Apostrophe Rule 4: Put an apostrophe before a plural s following single letters.

Put an apostrophe wherever adding an s to make a simple plural would be confusing, such as pluralizing a single letter.

How This Helps the Reader

The apostrophe helps the reader see these as plural forms of letters rather than as misspellings or typos.

What to Look for When Proofreading

In the rare case of using a plural form of a letter, separate the letter and its s with an apostrophe if you have omitted it.

In the example above, omitting the apostrophe makes the plural of the letter r appear as a typo.

Return to Quick Rules: Apostrophes

For more on apostrophes, see the following resources:

• Purdue OWL’s The Apostrophe (2021) along with its Exercise: Apostrophes (n.d.)
• The Punctuation Guide’s Apostrophe page (Penn, 2021b)
• The Grammar Book’s Apostrophes page and its Apostrophes Quiz 1 and Apostrophes Quiz 2 (Straus, 2014a)

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D.3.3: Colons

Colons and semicolons are often confused because of the similarities in both their names and form, though they perform quite different punctuation roles. A colon looks like a period stacked on top of another and is mainly used to equate information on either side of it somewhat like an equals sign (=) in math. A semicolon, on the other hand, looks like a period stacked on top of a comma. The semicolon usually separates independent clauses from one another in a compound sentence as an alternative to using a comma and a conjunction. They both have additional specific uses as we shall see below, starting with the colon.

Quick Rules: Colons

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common colon errors associated with each one.

Extended Explanations

Colon Rule 1.1: Put a colon at the end of a clause or phrase introducing a list.

Put colon after a clause or phrase that introduces a list formatted either as a series separated by commas in the sentence or a bulleted or numbered stack down the page.

How This Helps the Reader

The colon cues the reader to read the information following as a list of items in parallel delivering on the promise made in the clause or phrase preceding it.

What to Look for When Proofreading

Look for lists either in sentence form with each item separated by a comma or in the form of a numbered or bulleted list. If no colons separate the introductory clauses or phrases from the lists that follow, add them. If semicolons or commas introduce the lists (see Semicolon Rule 3 below), replace them with colons.

In the example above, the writer made the common mistake of confusing a semicolon for a colon. Fixing it is a simple matter of replacing one with the other. See the example correct sentence for Colon Rule 2.1 below for a handy mnemonic for getting the right punctuation in these cases.

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Colon Rule 1.2: Put a colon at the end of an opening salutation in formal emails and letters.

Put a colon at the end of the opening salutation line where you address the recipient by name at the opening of a formal email or letter. In a semiformal email, a comma at the end of the salutation is fine. If an email is formal, however, a comma follows the greeting word (e.g., Hello) and the colon follows the recipient’s name.

How This Helps the Reader

The colon cues the reader to read the message following the salutation that addresses them by name.

What to Look for When Proofreading

Look for either no punctuation used at the end of an opening salutation address or other punctuation inappropriate for the occasion, such as a comma in a letter’s salutation, or incorrect, such as a semicolon.

In the first incorrect example, a comma used at the end of an opening salutation addressing the reader in a letter is too informal for the given channel. This suggests to the professional reader that the writer isn’t up to date on business letter writing conventions. Modern business writers use a colon instead of a comma. Worse, the semicolon suggests that the writer is confused about the respective roles of colons and semicolons despite having had ample opportunity to learn them throughout their Enlgish-speaking lives.

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Colon Rule 2.1: Put a colon between an explanation and its introductory independent clause.

Put colon after an independent clause followed by a statement that explains in further detail what the introductory clause states in general. An independent clause is one that can stand on its own as a sentence beginning with a capital and ending with a period because it expresses a complete thought with a subject (doer) and a predicate. This colon usually stands for the causal transition phrase “—that is, . . . .”

How This Helps the Reader

The colon cues the reader to read the phrase or clause to the right of the colon as an explanation of what the clause to the left of it says.

What to Look for When Proofreading

Look for combination statement-explanation sentence structures with either no punctuation between them or the wrong punctuation such as a semicolon, comma, or long dash (em dash).

In the incorrect sentence above, the writer made the common mistake of using the long dash as multipurpose punctuation for any pause you hear in speech. Fixing the sentence is a simple matter of replacing the long dash with a colon. You could alternatively add “that is, ” between the long dash and “delete,” but the colon makes for a more concise sentence with two fewer words.

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Colon Rule 2.2: Put a colon between a quotation and its introductory independent clause if the latter is a complete sentence.

Put a colon after an independent clause that introduces a quotation. Like the clause followed by an explanation in Colon Rule 2.1 above, it must be a complete clause that can stand on its own before the colon and quotation.

How This Helps the Reader

The colon cues the reader to read the quotation to the right of the colon.

What to Look for When Proofreading

Look for quotations preceded by a complete independent clause. If they don’t have a colon separating them from the quotation, add one. Also, look for colons used to set up quotations when a comma is more appropriate, such as if the last word before the quotation is a verb, which would make the clause preceding the colon incomplete. In such cases, you would either replace the colon with a comma or rephrase the introductory fragment to make it an independent clause.

In the example above, the clause preceding the colon and quotation is a compound with a fragmentary second clause missing an object after the transitive verb “said,” whereas it would have to be a complete independent clause to use a colon. Correcting it would be a simple matter of replacing the colon with a comma (see Comma Rule 3.5 above). Alternatively, you could make the introductory clause a complete and independent one, meaning it could stand on its own as a sentence, then use a colon before the quotation.

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Colon Rule 2.3: Don’t put a colon before an explanation or quotation preceded by a fragment.

Don’t put a colon before an explanation or list if the clause that precedes it is not an independent one—that is, if it cannot stand on its own as a sentence.

What to Look for When Proofreading

Look for colons ending phrases or incomplete clauses with lists or explanatory statements following, and simply delete them or rephrase the incomplete clause as a complete one. The incorrect sentence at the end of Colon Rule 2.2 above exemplifies an incomplete clause preceding a quotation; below is one preceding a list:

In the example above, the colon ends an incomplete clause—incomplete because it has a subject and only half of the predicate. The verb “include” is transitive, which means that an object (a thing acted upon by the verb) must follow it (Simmons, 2007a). The objects here are gerunds, which are verbs in noun form ending in -ing (Simmons, 2018b) and are all on the other side of the colon, so the colon can just be deleted. Alternatively, the incomplete clause can be completed by changing the subject to “The following tasks” to set up the list and changing the verb to the intransitive “remain”—intransitive because it doesn’t take an object (Simmons, 2008).

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Colon Rule 3.1: Put a colon between a main title and its subtitle.

How This Helps the Reader

The colon distinguishes what should be known as the main title of the book, film, report, assignment, etc. Often this is a catchy, snappy handle for what to call it. The subtitle usually provides a little more practical information about what the work is about.

What to Look for When Proofreading

Look for titles that have any punctuation other than colons between main titles and subtitles. Often the cover of a book positions the subtitle below the main title and in a smaller font, in which case a colon must be added when transcribing the title into a document.

In the example above, the absence of punctuation separating the main title from the subtitle on the cover may have prompted the writer to make one up by using a slash. The convention for representing main titles and subtitles, however, is to separate them with a colon.

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Colon Rule 3.2: Put a colon between publisher locations and names in bibliographical references.

Put a colon between the location and company name of a publisher in APA References.

How This Helps the Reader

The colon is merely a convention for separating the publisher location and name. Readers like to know if the book is published in the major centres like New York or London, or if they’re more local like Toronto or Vancouver.

What to Look for When Proofreading

Look for the part in bibliographical references of books where the publisher information is given. If any punctuation other than a colon separates them, replace it with a colon.

In the example above, the comma is non-standard punctuation separating the city where the book publisher is based and the name of the publisher. It must be replaced with a colon.

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Colon Rule 3.3: Put a colon between numbers in ratios and times.

Put a colon between numbers in mathematical ratios and to separate hours, minutes, and seconds when indicating time.

How This Helps the Reader

The colon expresses mathematical relationships and the division of units between numbers in a space-efficient manner.

What to Look for When Proofreading

Look for ratios and times to ensure that a colon is being used and that there are no spaces between it and the numbers on either side.

In the example above, errors in spacing and using non-standard punctuation are easily corrected by deleting spaces between the numbers and colons in the first time written and using colons instead of periods in the second.

Return to Quick Rules: Colons

For more on colons, see the following resources:

• Purdue OWL’s Punctuation—Semicolons, Colons, and Parentheses page (Cimisko, 2021)
• The Punctuation Guide’s Colon page (Penn, 2011c)
• The Grammar Book’s Colons page and its Semicolons and Colons Quiz 1 and Semicolons and Colons Quiz 2 at the bottom (Straus, 2015a)

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D.3.4: Semicolons

Semicolons and colons are often confused because of the similarities in both their names and form, though they perform quite different punctuation roles. A semicolon looks like a period stacked on top of a comma and is mainly used to separate independent clauses from one another in a compound sentence as an alternative to using a comma and a conjunction. A colon, on the other hand, looks like a period stacked atop another and is mainly used to equate information on either side of it somewhat like an equals sign (=) in math. They both have additional specific uses as we saw above with colons in §D.3.3 above and will now see with semicolons.

Quick Rules: Semicolons

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common semicolon errors associated with each one.

Extended Explanations

Semicolon Rule 1: Put a semicolon between related independent clauses to make a compound sentence.

Put a semicolon between independent clauses whose content is so closely related that it makes sense to keep them in the same sentence, though they have different grammatical subjects (doers of the action). An independent clause is one that can stand on its own as a complete sentence because it has a subject (doer) and predicate (action). A compound sentence joins two independent clauses either with a comma and coordinating conjunction (and, but, so, etc.;) or with a semicolon. Doing neither would make a run-on sentence, and using only a comma between the clauses would make a comma splice. Use a semicolon in compound sentences where none of the seven coordinating conjunctions is appropriate to use or where you need to be as concise as possible and can do without the conjunction without sacrificing clarity.

How This Helps the Reader

The semicolon helps the reader see where one clause ends and another (with a different grammatical subject) begins. It also signals that these are two closely related ideas worth joining in the same sentence.

What to Look for When Proofreading

Look for compound sentences punctuated with anything other than a semicolon (e.g., a comma, which makes a comma splice; see §D.2.1.1) or with no punctuation at all between them (run-on sentences; see §D.2.1.2). For this you really must know sentence structure well enough to spot the grammatical subject of a main (a.k.a. independent) clause so that you can tell if a second subject begins a new independent clause within a sentence but without the necessary punctuation preceding it.

The incorrect sentence above is a comma splice because it uses only a comma to separate two independent clauses (see Comma Rule 1.2). The error is easier to spot if you imagine deleting the conjunctive adverb however. Replacing the comma with a semicolon and adding a comma after the conjunctive adverb easily fixes the problem.

The incorrect sentence above is a run-on sentence because it contains two independent clauses without any punctuation between them. Adding a semicolon quickly makes the sentence a properly punctuated compound sentence.

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Semicolon Rule 2: Put a semicolon between sub-lists in a series of lists in a sentence.

Use semicolons as a “super comma” between groups of items in a long list of items arranged in a sentence.\

How This Helps the Reader

The semicolon helps the reader see subgroups within a long list that would be confusing if it included ands between the two last items in each subgroup throughout.

What to Look for When Proofreading

Look for sentences that contain long lists and see if there are internal groupings that can be separated with semicolons rather than commas.

In the incorrect example above, the long list of items is internally organized into groups of family and professional roles, as well as personal qualities. To help the reader follow these divisions as they switch from one group to another, the semicolon acts as a “super comma.”

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Semicolon Rule 3: Don’t put a semicolon where a colon should be used.

Don’t use semicolons as if they were interchangeable with colons. They are different punctuation marks performing different functions. Review the semicolon rules above and compare with §D.3.3 on uses for colons.

What to Look for When Proofreading

Look for semicolons and determine if they are being used appropriately in the manner described in the rules above, or if they are actually performing the functions of colons explained and exemplified in §5.3.3 above. You can jump straight to every instance of a semicolon throughout your document by performing a word search (ctrl. + f) and just typing in a semicolon (;).

In the incorrect example above, the semicolon is being used to introduce a list of items, which is the function of a colon (see Colon Rule 1). Simply replacing the semicolon with a colon corrects the error.

Return to Quick Rules: Semicolons

For more on colons, see the following resources:

• Purdue OWL’s Punctuation—Semicolons, Colons, and Parentheses page (Cimisko, 2021)
• The Punctuation Guide’s Semicolon page (Penn, 2011d)
• The Grammar Book’s Semicolons page and its Semicolons and Colons Quiz 1 and Semicolons and Colons Quiz 2 at the bottom (Straus, 2014b)

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D.3.5: Parentheses

Parentheses are often confused with brackets because they look alike and perform similar functions. Parentheses are curved lines that surround qualifying, non-essential elements, whereas brackets are squared, open-ended boxes used for very specific parenthetical situations. Let’s take a closer look at the occasions for which we would use parentheses rather than brackets or even commas.

Quick Rules: Parentheses

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common parentheses errors associated with each one.

Extended Explanations

Parentheses Rule 1.1: Put parentheses around qualifying interjections of lesser importance within and between sentences.

Use parentheses around interjections within a sentence where using parenthetical commas would lead to confusion. You can also use parentheses around an entire sentence that offers an aside that helps explain something said in the sentence previous. Parentheses always come in pairs: an opening parenthesis signals the beginning of an interjection of lesser importance, and a closing parenthesis signals the return to the sentence proper. When used around an entire sentence, the closing parenthesis goes after the sentence-ending period; otherwise, it goes before.

How This Helps the Reader

The parentheses guide the reader towards reading the words, phrases, and clauses surrounded by them as being of lesser importance but still offering insight into what comes immediately before them.

What to Look for When Proofreading

Look to make sure that the parentheses you use genuinely set off words, phrases, or clauses that help explain those that came before them, and that the parentheses both open and close. If you use parentheses around a whole sentence, ensure that the closing parenthesis goes to the right of the period rather than to the left.

The incorrect example above uses parenthetical commas to set off the Latin name of the insect referred to in the first clause, then uses a Rule 1.1 comma to crowd the area with commas. Parentheses would be more appropriate here, as well as in the second incorrect example that omits the closing parenthesis. The second sentence also places the parenthetical element at the end of the clause rather than where it should be: immediately after the common name of the insect it explains.

The incorrect sentence places the closing parenthesis to the left of the period ending the parenthetical sentence; if the parenthetical sentence were deleted along with the parentheses, the period would be stranded between sentences. Correcting this involves simply moving the period so it goes to the left of the closing parenthesis.

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Parentheses Rule 1.2: Don’t use parentheses where parenthetical commas would do.

Don’t overuse parentheses, especially where parenthetical commas would be more appropriate. Recall that, according to Comma Rule 3.1, commas can surround parenthetical, non-essential words, phrases, and clauses added to explain immediately what came before. Whether you use commas or parentheses, the sentence must make grammatical sense without the interjected element. The problem with overusing parentheses, however, is that it clutters up your writing with distracting asides, so the less conspicuous comma is preferable in situations where a parenthetical element doesn’t need full parentheses.

What to Look for When Proofreading

Look to make sure that the parentheses you use can’t be replaced with commas without causing confusion. In other words, if the parenthetical element follows Comma Rule 3.1 and doesn’t involve other types of commas covered by the other rules, then use commas instead of parentheses.

The incorrect example above includes a restrictive relative clause beginning with which, which is a perfect example of a non-essential parenthetical clause that we saw being set off from the main clause in Comma Rule 3.1 above. In this case, commas would be better to use than parentheses.

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Parentheses Rule 2: Put parentheses around in-text citations crediting research sources in APA and MLA documentation styles.

How This Helps the Reader

The parentheses tell the reader that the quotation, paraphrase, or summary came from the author or authors named within the parentheses. The reader can then consult the References section at the end of the document and easily find the full bibliographical reference for that source by searching out the same author last name in the alphabetical list of source authors. When citing multiple works by the same author, the year of publication in the citation allows the reader to distinguish between them.

What to Look for When Proofreading

Look to make sure that you use parentheses rather than brackets if your documentation style is APA or MLA. IEEE, on the other hand, does use brackets, albeit with a numerical citation rather than author and year.

The incorrect sentence above uses brackets rather than parentheses to mark off an in-text citation. Use parentheses for APA or MLA in-text citations.

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For more on parentheses, see the following resources:

• Purdue OWL’s Punctuation—Semicolons, Colons, and Parentheses page (Cimisko, 2021)
• The Punctuation Guide’s Parentheses page (Penn, 2011e)
• The Grammar Book’s Parentheses and Brackets page and its Question Marks, Quotation Marks, and Parentheses Quiz 1 linked at the bottom (Straus, 2014c)

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D.3.6: Brackets

Brackets are often confused with parentheses because they look alike and perform similar functions. Brackets are squared open-ended boxes used for more specific parenthetical situations than their curved-line counterparts. Let’s take a closer look at the occasions for which we would use brackets rather than parentheses.

Quick Rules: Brackets

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common bracket errors associated with each one.

Extended Explanations

Brackets Rule 1.1: Put brackets around changes or additions to the wording of quotations.

How This Helps the Reader

The brackets indicate what changes the writer makes to a quotation, whether to lend clarity to the original wording or to make it grammatically consistent with the sentence around it. Doing so shows a concern for both quoting accurately and writing correctly. Sneaking in some changes to a quotation to suit your purposes is called misquoting. Sometimes the additions draw attention to errors in the original, such as corrections to the spelling or the use of “[sic],” short for the Latin sic erat scriptum (“thus was it written”), to preserve the author’s error.

What to Look for When Proofreading

Ensure that quotations are exact transcriptions of the original to avoid misquoting. If you find any intentional changes, surround them with brackets. Ensure also that any errors in the original quotation are preserved but identified with “[sic]” immediately following.

The incorrect example above contains a quotation that is grammatically incorrect in its original form. Adding “[sic]” ensures the reader that the critical writer is well aware that, with “think” being a verb, “different” would have to be the adverb “differently” to be correct. Adding the -ly ending in brackets takes a more corrective approach to the error.

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Brackets Rule 1.2: Don’t put brackets around what should have parentheses.

What to Look for When Proofreading

Ensure that the brackets you use don’t follow either of the parentheses rules explained in §D.3.5 above.

The incorrect example above mistakenly uses brackets around the parenthetical Latin name of the insect identified just before by its common name. Following Parentheses Rule 1.1, however, you would just replace the brackets with parentheses.

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Brackets Rule 2: Put brackets around parenthetical elements within parentheses.

Use brackets whenever you have parenthetical elements within a phrase or clause that is already surrounded by parentheses.

How This Helps the Reader

Brackets help the reader keep track of nested parenthetical elements. Switching to brackets for parenthetical elements within parentheses also helps avoid the awkwardness of “double-chin” parentheses such as “)).”

What to Look for When Proofreading

Look to make sure that you don’t double up parentheses with “))” anywhere in your document.

In the incorrect sentence above, parentheses are used within parentheses. Simply replace the inner parentheses with brackets.

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Brackets Rule 3: Put brackets around IEEE-style numerical in-text citations crediting research sources.

How This Helps the Reader

The brackets tell the reader that the quotation, paraphrase, or summary came from the research source numbered within the brackets. The reader can then consult the References section at the back and easily find the full bibliographical reference for that source by the corresponding number (see §3.5.4 above for more on IEEE-style citations and references).

What to Look for When Proofreading

Look to make sure that you use brackets rather than parentheses if your documentation style is IEEE, as opposed to APA or MLA, which use parentheses.

In the incorrect example above, parentheses are used rather than brackets to mark off an in-text citation. The correct in-text citation style for IEEE is to use brackets instead.

• Return to Quick Rules: Brackets

For more on brackets, see the following resources:

• The Punctuation Guide’s Brackets page (Penn, 2011f)
• The Grammar Book’s Parentheses and Brackets page and Question Marks, Quotation Marks, and Parentheses Quiz 1 linked at the bottom (Straus, 2014c)

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D.3.7: Quotation Marks

Quotation marks are mostly used to set reported speech or text apart from the author’s words. They essentially say, “These are someone else’s words, not mine.” But some writers confuse double quotation marks (simply called “quotation marks” here) with single quotation marks, as well as misplace punctuation around quotation marks, so let’s focus on when and how to use quotation marks, as well as single quotation marks, properly. Since the absence of quotation marks when using research sources in your document can result in plagiarism (see §3.4.1 and §3.5.1 above), knowing how to use them correctly is vitally important to your success as a student and professional.

Quick Rules: Quotation Marks

Click on the rules below to see further explanations, examples, advice on what to look for when proofreading, and demonstrations of how to correct common quotation mark errors associated with each one.

• The Purdue OWL’s series of modules, starting with How to Use Quotation Marks (Conrey, Pepper, & Brizee, 2021) and ending with the exercises in the fifth module
• The Grammar Book’s Quotation Marks page and its Question Marks, Quotation Marks, and Parentheses Quiz 1 and Question Marks, Quotation Marks, and Parentheses Quiz 2 linked at the bottom (Straus, 2007a).

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D.3.8: Hyphens

Using hyphens between two or more words in combination helps the reader treat them as if they were one word when the words around them would create ambiguity without the hyphen(s). We do this especially with compound modifiers, which are two or more adjectives that modify the same noun in combination. For instance, if you said that there was funding available for small business owners, does that mean funding is only available for people who are under five feet tall? (In that case, “business owners” is read as a compound noun and “small” is the adjective modifying it.) If you mean that funding is available for business owners who employ fewer than 15 people, then you want to use the compound-modifier hyphen to pair up “small” and “business” so that they are read as if they were one adjective modifying the noun “owners”: small-business owners. Hyphens help the reader by guiding them toward what words to pair up when it could go either way.

The same is true of hyphens used in compound nouns. Saying, “It was a light year” means something completely different from “It was a light-year.” In the first case, you’re saying that nothing much happened that year; in the second, you’re saying that something spanned nearly ten trillion kilometres. Hyphens matter!

• https://ruthlesseditor.com/compound-modifiers/
• http://www.btb.termiumplus.gc.ca/tcdnstyl-chap?lang=eng&lettr=chapsect2&info0=2

D.3.8.1: Compound-modifier Hyphens

The most common use of hyphens is for compound modifiers—that is, two or more adjectives that must be read in combination before a noun they describe. In fact, the hyphen you see between “compound” and “modifier” in the sentence above exemplifies how this works: since both of those words together (and in that order only) modify the noun “hyphen” (“modify” meaning that they tell you what kind of hyphen it is), the hyphen helps the reader identify which words functions as modifiers and which as nouns, since “modifier” in this case behaves as an adjective rather than a noun. Without the hyphen, the reader might make the mistake of taking “modifier hyphen” as a compound noun, as in the case of “small business owners” above.

If you were to say that the USSR was the first second world country to de-communize, the combination “first second” would surely trip up the reader. But pairing “second” and “world” with a hyphen resolves the ambiguity to say “The USSR was the first second-world country to de-communize.”

Table D.3.8.1a: Common First-term Nouns in Compound Modifiers

Table D.3.8.1b: Common Adverbs in Compound Modifiers

Exception: Don’t add hyphens after adverbs ending in -ly.

Table D.3.8.1c: Common Prefixes Making Compound Modifiers

Table D.3.8.1d: Common Middle-term Prepositions in Three-part Compound Modifiers

Table D.3.8.1e: Common Three-part Compound-modifier Phrases

Table D.3.8.1f: Common Foreign-phrase Compound Modifiers

Don’t hyphenate more recently imported foreign phrases that are still italicized.

Table D.3.8.1g: Common End-term Nouns in Compound Modifiers

Table D.3.8.1h: Common Past-participles Following Nouns

Table D.3.8.1i: Common End-term Present-participle and Gerund Compound-modifier Adjectives

Table D.3.8.1j: Common End-term Preposition Compound-modifier Adjectives

Table D.3.8.1k: Common Number + Time-period Compound Modifiers

But some have become one word, like handwritten and handmade, standalone

Compound adjectival Numbers

Suspended Hyphens

Prefixes

• Big hair in the mid-1980s
• Populism results in new accusations of anti-Americanism (because “America” is capitalized)
• My ex-girlfriend and I haven’t spoken in a decade
• I re-wrote the essay
• e-mail
• Not with adverbs ending in -ly

Compound Nouns

Again, anything starting with “self-” (e.g., self-starter, self-esteem, self-care), “great-” (e.g., great-grandmother, great-uncle), or ending with “-in-law” (e.g., mother-in-law, sister-in-law) and numbers above 20 (twenty-one, forty-three). If someone said that you have poor people skills, does that mean you have skill in dealing with poor people? By hyphenating “people-skills,” they make it clear that you could be better at dealing with people in general.

Table D.3.8.2a: Common Compound Units of Measurement

Table D.3.8.2b: Common Prefixes Making Compound Nouns

Table D.3.8.2c: Common Three- or Four-term Compound Nouns

Some words have become one word like headache, checkout, chequebook, uproar, downpour, input, sunrise, clearinghouse, bookkeeper, housekeeper, sightseeing, shipbuilding, cabinetmaker, blackboard, redhead, workplace, and even email

• How to Hyphenate a Compound Noun:  https://www.capstoneediting.com.au/blog/how-to-hyphenate-a-compound-noun

Compound Verbs

Usually pairing a noun with a verb, but some are now combined into one word.

Source: Grammar Usage – Compound Verbs (Jamieson, 2010)

Return to the beginning of the Hyphens section

For more on hyphens, see the following resources:

• Purdue OWL’s Hyphen Use (Conrey & Stolley, 2021)
• The Punctuation Guide’s Hyphens page (Penn, 2011g)
• The Grammar Book’s Hyphens page and its Hyphens Quiz 1 and Hyphens Quiz 2 at the bottom of the page (Straus, 2007b)

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D.3.9: Long Dashes

For more on long dashes, see the following resources:

• Purdue OWL’s Punctuation—Hyphens and Dashes page (Cimasko, 2021)
• The Punctuation Guide’s Hyphen and Dashes page (Penn, 2011h)
• The Grammar Book’s Dashes page (Straus, 2018b)

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D.3.10: Question Marks

Question marks obviously follow questions. However, if the question is a polite request for action rather than one where a Yes or No answer is expected—i.e., a rhetorical question—end the sentence with a period rather than a question mark (Jamieson, 2014).

For more on long dashes, see the following resources:

• The Punctuation Guide’s Question Mark page (Penn, 2012)
• The Grammar Book’s Question Marks page and its Question Marks, Quotation Marks, and Parentheses Quiz 1 and Question Marks, Quotation Marks, and Parentheses Quiz 2 linked at the bottom (Straus, 2014d)

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D.3.11: Exclamation Marks

For more on exclamation marks, which should be used sparingly, see the following resources:

• The Punctuation Guide’s Exclamation Point page (Penn, 2011i)
• The Grammar Book’s Exclamation Points page (Straus, 2015b)

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D.3.12: Periods

For more on periods, see the following resources:

• The Punctuation Guide’s Period page (Penn, 2011h)
• The Grammar Book’s Periods page (Straus, 2014e)

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