Definition of: prefix

(prē′fiks) noun
1. Gram. A non–separable syllable, or syllables, affixed to the beginning of a word to modify or alter the meaning, as pre– in prefix, be– in behead, dis– in disagree, re– in renew, post– in postwar, un– in unhorse, etc.
2. Something placed before, as a title before a noun. Compare SUFFIX.
—v.t. (prē·fiks′)
1. To put or attach before or at the beginning; add as a prefix: opposed to postfix.
2. Obs. To arrange or settle beforehand. [<OF prefixer <L praefixus, pp. of praefigere <prae- before + figere fix]
—pre′fix·al adjective
—pre′fix·al·ly adverb
—pre·fix·ion (prē·fik′shən) noun