A prefix is an affix which is placed before the root of a word. Particularly in the study of languages, a prefix is also called a preformative, because it alters the form of the words to which it is affixed. For an example:
- unhappy : un is a negative or antonymic prefix.
- prefix, preview : pre is a prefix, with the sense of before
- redo, review. : re is a prefix meaning again.
The word prefix is itself made up of the stem fix (meaning attach, in this case), and the prefix pre- (meaning "before"), both of which are derived from Latin roots.