Affix, a grammatical element that is combined with a word, stem, or phrase to produce derived or inflected forms. There are three main types of affixes: prefixes, infixes, and suffixes. A prefix occurs at the beginning of a word or stem (sub-mit, pre-determine, un-willing); a suffix at the end (wonder-ful, depend-ent, act-ion); and an infix occurs in the middle.