A morpheme is the smallest unit of speech that has meaning. It cannot be divided into anything smaller without changing meaning or becoming completely meaningless. Throughout different uses, it is basically stable and will keep its same basic meaning. A word or part of a word can be a morpheme.
The two types are bound and free morphemes. The first cannot stand alone without helpers to help give it meaning. “Free” have their own meaning and can function with no assistance. Essentially, “free” are words and “bound” are parts of a word.
Bound: prefixes, affixes and suffixes are some common types, such as pre-, ante-, post-, -less, -er and -ism.
Pre-order, antebellum, post-war, waterless, cleaner, vegetarianism
Free: words that cannot be made into a smaller unit and are often the root of a larger word. Trip, leaf, ship, car, sheep, cat, box
Content and Function
Free types can be placed into two categories: content and function. Content words, also known as lexical words, provide a sentence with information and are required for text to convey any ideas to a reader. Function words, in contrast, accomplish a purpose rather than offer any meaning in themselves.
Content types can be nouns, adverbs, adjectives and main verbs and they always have their own meaning. Each of the above “free” examples are content types.
Function types can be pronouns, articles, determiners, prepositions, auxiliary verbs, modals, conjunctions and so on. If, and, the, that and she are all examples, and none can be made smaller.