Prefixes, suffixes, and words are examples of morphemes.
Morphemes are the smallest units in a language that have a meaning. Suffixes and prefixes add a new meaning to a word - by adding the prefix re- to the verb do, you get a new verb - redo, which has a new meaning. Simple words, such as fun, are also considered to be morphemes, but if they are complex, such as realizations, they are not morphemes, but rather consist of numerous morphemes.