The last unit talked about inflection, which is one of the jobs that morphology can do. The other big job that morphemes have is a derivation. The derivation is the process of creating a new word. The new, derived word is related to the original word, but it has some new component of meaning to it, and often it belongs to a new category.
One of the most common ways that English derives new words is by affixing a derivational morpheme to a base. For example, if we start with a verb that describes an action, like teach and we add the morpheme –er, we derive a morphologically complex noun, teacher, that refers to the person who does the action of teaching. That same -er morpheme does the same job in singer, dancer, baker, and writer.
If we start with an adjective like happy and add the suffix –ness, we derive the noun that refers to the state of being that adjective, happiness.
Adding the suffix –ful to a noun derives an adjective, like hopeful.
Adding the suffix–ize to an adjective like final derives a verb like finalize.
Notice that each of the morphologically complex derived words is related in meaning to the base, but it has a new meaning of its own. English also derives new words by prefixing, and while adding a derivational prefix does lead to a new word with a new meaning, it often doesn’t lead to a category change.
Each instance of derivation creates a new word, and that new word could then serve as the base for another instance of derivation, so it’s possible to have words that are quite complex morphologically.
For example, say you have a machine that you use to compute things; you might call it a computer (compute + -er).Then if people start using that machine to perform a task, you could say that they’re going to computerize (computer + -ize) that task. Perhaps the computerization (computerize + -ation) of that task makes it much more efficient. You can see how many words have many steps in their derivations.
An interesting thing to note is that once a base has been inflected, then it can no longer go through any derivations. We can inflect the word computer so that we can talk about plural computers, but then we can’t do derivation on the plural form (*computers-ize). Likewise, we can add tense inflection to the verb computerize and talk about how yesterday we computerized something, but then we can’t take that inflected form and use it as the base for a new derivation (*computerized-ation). Inflection always occurs as the last step in word formation.