Prefixes Tools A B ab- from; away from ad- to; motion toward; addition to aero- air amphi- both; around an- not ante- before anti- against; opposite; reverse ap- to; nearness to auto- self bene- good bi- two circum- around co-, con- together contra- against de- opposite of; away from; former dis- opposite ex- out; beyond; away from; former extra- outside, beyong, besides for- not fore- before hyper- more than normal; too much il- not im- into or not in- not; go into inter- among; between ir- not mal- wrong; bad mis- wrong; bad; no; not non- not; opposite of ob- against per- through post- after pre- before pro- before; for; in support of or forward re- back; again retro- backward se- apart self- on the self semi- half; partly sub- under; beneath super- over sur- over; above trans- across; over ultra- extremely un- not; lack of; opposite