2.1 Commas
One of the punctuation clues you may encounter when reading is the comma. A comma is a punctuation mark that indicates a pause in a sentence or a separation of things in a list. Commas can be used in a variety of ways. Look at some of the following sentences to see how you might use a comma when writing a sentence.
- Introductory word: Personally, I think the practice is helpful.
- Lists: The barn, the tool shed, and the back porch were destroyed by the wind.
- Coordinating adjectives: He was tired, hungry, and late.
- Conjunctions in compound sentences: The bedroom door was closed, so the children knew their mother was asleep.
- Interrupting words: I knew where it was hidden, of course, but I wanted them to find it themselves.
- Dates, addresses, greetings, and letters: The letter was postmarked December 8, 1945.
Commas after an Introductory Word or Phrase
You may notice a comma that appears near the beginning of the sentence, usually after a word or phrase. This comma lets the reader know where the introductory word or phrase ends and the main sentence begins.
Without spoiling the surprise, we need to tell her to save the date.
In this sentence, without spoiling the surprise is an introductory phrase, while we need to tell her to save the date is the main sentence. Notice how they are separated by a comma. When only an introductory word appears in the sentence, a comma also follows the introductory word.
Ironically, she already had plans for that day.
Commas in a List of Items
When you want to list several nouns in a sentence, you separate each word with a comma. This allows the reader to pause after each item and identify which words are included in the grouping. When you list items in a sentence, put a comma after each noun, then add the word and before the last item. However, you do not need to include a comma after the last item.
We’ll need to get flour, tomatoes, and cheese at the store.
The pizza will be topped with olives, peppers, and pineapple chunks.
Commas and Coordinating Adjectives
You can use commas to list both adjectives and nouns. A string of adjectives that describe a noun is called a coordinating adjective. These adjectives come before the noun they modify and are separated by commas. One important thing to note, however, is that, unlike listing nouns, the word and does not always need to be before the last adjective.
It was a bright, windy, clear day.
Our kite glowed red, yellow, and blue in the morning sunlight.
Commas before Conjunctions in Compound Sentences
Commas are sometimes used to separate two independent clauses. The comma comes after the first independent clause and is followed by a conjunction, such as for, and, or but. For a full list of conjunctions, see Chapter 7: Writing Basics: Sentence Writing in Putting the Pieces Together.
He missed class today, and he thinks he will be out tomorrow, too.
He says his fever is gone, but he is still very tired.
Commas before and after Interrupting Words
In conversations, you might interrupt your train of thought by giving more details about what you are talking about. In a sentence, you might interrupt your train of thought with a word or phrase called Interrupting words. Interrupting words can come at the beginning or middle of a sentence. When the interrupting words appear at the beginning of the sentence, a comma appears after the word or phrase.
If you can believe it, people once thought the sun and planets orbited around Earth.
Luckily, some people questioned that theory.
When interrupting words come in the middle of a sentence, they are separated from the rest of the sentence by commas. You can determine where the commas should go by looking for the part of the sentence that is not essential for the sentence to make sense.
An Italian astronomer, Galileo, proved that Earth orbited the sun.
We have known, for hundreds of years now, that the Earth and other planets exist in a solar system.
Commas in Dates, Addresses, and the Greetings and Closings of Letters
You also use commas when you write the date, such as in cover letters and e-mails. Commas are used when you write the date, when you include an address, and when you greet someone.
If you are writing out the full date, add a comma after the day and before the year. You do not need to add a comma when you write the month and day or when you write the month and the year. If you need to continue the sentence after you add a date that includes the day and year, add a comma after the end of the date.
The letter is postmarked May 4, 2024.
Her birthday is May 5.
He visited the country in July 2023.
I registered for the conference on March 7, 2020, so we should get our tickets soon.
You also use commas when you include addresses and locations. When you include an address in a sentence, be sure to place a comma after the street and after the city. Do not place a comma between the province (or state) and the postal/zip code. Like a date, if you need to continue the sentence after adding the address, simply add a comma after the address.
We moved to 4542 Boxcutter Lane, London, Ontario N5Y 4R6.
After moving to Toronto, Ontario, Eric used public transportation to get to work.
Greetings are also separated by commas. When you write an e-mail or a letter, you add a comma after the greeting word or the person’s name. You also need to include a comma after the closing, which is the word or phrase you put before your signature.
Hello,
I would like more information about your job posting.
Thank you,
Anita Al-Sayf
Dear Mrs. Al-Sayf,
Thank you for your letter. Please read the attached document for details.
Sincerely,
Jack Fremont
Key Takeaways
- Punctuation marks provide visual cues to readers to tell them how to read a sentence. Punctuation marks convey meaning.
- Commas indicate a pause or a list in a sentence.
- A comma should be used after an introductory word to separate this word from the main sentence.
- A comma comes after each noun in a list. The word and is added before the last noun, which is not followed by a comma.
- A comma comes after every coordinating adjective except for the last adjective.
- Commas can be used to separate the two independent clauses in compound sentences as long as a conjunction follows the comma.
- Commas are used to separate interrupting words from the rest of the sentence.
- When you write the date, you add a comma between the day and the year. You also add a comma after the year if the sentence continues after the date.
- When they are used in a sentence, addresses have commas after the street address and the city. If a sentence continues after the address, a comma comes after the postal/zip code.
- When you write a letter, you use commas in your greeting at the beginning and in your closing at the end of your letter.
“10.1 Commas” from Putting the Pieces Together by Andrew M. Stracuzzi and André Cormier is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.—Modifications: Removed Learning Objectives and Exercises.
