A prefix is an affix which is placed before the stem of a word. Adding it to the beginning of one word changes it into another word. For example, when the prefix un- is added to the word happy, it creates the word unhappy. 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. Prefixes, like other affixes, can be either inflectional, changing the syntactic category, or derivational, changing either the lexical category or the semantic meaning. In English, there are no inflectional prefixes. Prefixes, like all other affixes, are bound morphemes. 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.