Prefixes

A prefix is placed at the beginning of a word to modify or change its meaning.

This is a list of the most common prefixes in English, together with their basic meaning and some examples. You can find more detail or precision for each prefix in any good dictionary. The origins of words are extremely complicated. You should use this list as a guide only, to help you understand possible meanings. But be very careful, because often what appears to be a prefix is not a prefix at all. Note also that this list does not include elements like "auto-" or " bio-", because these are "combining forms", not prefixes.

Prefix		Meaning	Examples
a-	also an-	not, without	atheist, anaemic
a-		to, towards	aside, aback
		in the process of, in a particular state	a-hunting, aglow
a-		of	anew
		completely	abashed
ab-	also abs-	away, from	abdicate, abstract
ad-	also a-, ac-, af-, ag- al-, an-, ap-, at- as-, at-	movement to, change into, addition or increase	advance, adulterate, adjunct, ascend, affiliate, affirm, aggravate, alleviate, annotate, apprehend, arrive, assemble, attend
ante-		before, preceding	antecedent, ante-room
anti-	also ant-	opposing, against, the opposite	anti-aircraft, antibiotic, anticlimax, Antarctic
be-		all over, all around	bespatter, beset
		completely	bewitch, bemuse
		having, covered with	bejewelled
		affect with (added to nouns)	befog
		cause to be (added to adjectives)	becalm
com-	also co-, col-, con-, cor-	with, jointly, completely	combat, codriver, collude, confide, corrode
contra-		against, opposite	contraceptive
counter-		opposition, opposite direction	counter-attack, counteract
de-		down, away	descend, despair, depend, deduct
		completely	denude, denigrate
		removal, reversal	de-ice, decamp
dia-	also di-	through, across	diagonal
dis-	also di-	negation, removal, expulsion	disadvantage, dismount, disbud, disbar
en-	also em-	put into or on	engulf, enmesh
		bring into the condition of	enlighten, embitter
		intensification	entangle, enrage
ex-	also e-, ef-	out	exit, exclude, expand
		upward	exalt, extol
		completely	excruciate, exasperate
		previous	ex-wife
extra-		outside, beyond	extracurricular
hemi-		half	hemisphere
hyper-		beyond, more than, more than normal	hypersonic, hyperactive
hypo-		under	hypodermic, hypothermia
in-	also il-, im-	not, without	infertile, inappropriate, impossible
	also il-, im-, ir-	in, into, towards, inside	influence, influx, imbibe
infra-		below	infrared, infrastructure
inter-		between, among	interact, interchange
intra-		inside, within	intramural, intravenous
non-		absence, negation	non-smoker, non-alcoholic
ob-	also oc-, of-, op-	blocking, against, concealing	obstruct, occult, offend, oppose
out-		surpassing, exceeding	outperform
		external, away from	outbuilding, outboard
over-		excessively, completely	overconfident, overburdened, overjoyed
		upper, outer, over, above	overcoat, overcast
peri-		round, about	perimeter
post-		after in time or order	postpone
pre-		before in time, place, order or importance	pre-adolescent, prelude, precondition
pro-		favouring, in support of	pro-African
		acting for	proconsul
		motion forwards or away	propulsion
		before in time, place or order	prologue
re-		again	repaint, reappraise, reawake
semi-		half, partly	semicircle, semi-conscious
sub-	also suc-, suf-, sug-, sup-, sur-, sus-	at a lower position	submarine, subsoil
		lower in rank	sub-lieutenant
		nearly, approximately	sub-tropical
syn-	also sym-	in union, acting together	synchronize, symmetry
trans-		across, beyond	transnational, transatlantic
		into a different state	translate
ultra-		beyond	ultraviolet, ultrasonic
		extreme	ultramicroscopic
un-		not	unacceptable, unreal, unhappy, unmanned
		reversal or cancellation of action or state	unplug, unmask
under-		beneath, below	underarm, undercarriage
		lower in rank	undersecretary
		not enough	underdeveloped