ab-, a-, abs-

EX: abduct, abnormal, avert, abstract

NOTE: This prefix is never assimilated, so do not confuse it with a followed by a double consonant, which is from ad-.

ad-, ac-, etc

EX: adopt, admire, access, aggression, attract, allocate, ascend

NOTE: Occasionally this prefix appears simply as a-, usually before -sc-, -sp-, and-st-; e.g., aspire, ascribe. When in doubt, however, assume that the prefix a- is a form of ab-, "away."

ambi-

EX: ambidextrous

ante-

EX: anteroom, antecedent

NOTE: Do not confuse this with anti-, a Greek prefix meaning "against."

circum-

EX: circumference, circumscribe

con-, com-, co-, etc

EX: connect, conduct, compose, compress, collect, correspond, co-operate

contra-, contro-, counter-

EX: contradict, controversy, counteract

de-

EX: descend, dejected

dis-, di-, dif-

EX: dispute, disable, divert, divorce, differ

ex-, e-, ef-, etc

EX: expel, exasperate, eloquent, evade, efficient

NOTE: In English, when ex- precedes a base beginning with s, the s is dropped. EX: expect, execute

extra-, extro-

EX: extraordinary, extrovert

in-, im-, etc., [en-], [em-]

EX: inject, impose, impel, illuminate, irrigate, endure, embrace

in-, im-, etc., ig- before n

EX: ineffective, imminent, immoral, impartial, illegal, irresponsible, ignoble, ignore

infra-

EX: infrared

inter-

EX: interrupt, intercept

intra-, intro-

EX: intramural, intravenous, introduce

non-

EX: nonresident

NOTE: This prefix in less emphatic than in- or the native English un-; compare nonreligious and irreligious, non-American and un-American.

ob-

EX: obstruct, obstacle, occur, offer, oppress

per-

EX: permeate, persecute, perfect, perjury

post-

postpone, postscript

pre-

EX: prevent, predict

pro-

EX: promote, produce

re-, red- (before vowels)

EX: renew, recede, recall, redemption

retro-

EX: retroactive

se-, sed- (before vowels)

EX: secede, segregate, sedition

sub-, sus-, suc-, etc

EX: submerge, submarine, suspend, sustain, succumb, suffer, support

super-, [sur-]

EX: superhuman, superfluous, surreal, surcease

trans-, tran-, tra-

EX: transfer, transparent, transcend, transcribe, traverse, travesty

ultra-

EX: ultraviolet, ultramodern