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. ... Prefixes, like all other affixes, are usually bound morphemes.

Is a prefix considered a word?

Prefixes and suffixes are both kinds of affixes. That is, they are word parts that attach to the beginning or end of a word or word base (a word stripped down to its simplest form) to produce a related word or an inflectional form of a word.

Can a prefix be the whole word?

There are no absolute rules for when to use a hyphen or when to write a prefixed word as one whole word (see the examples in the table).