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English prefixes are affixes (i.e., bound morphemes that provide lexical meaning) that are added before either simple roots or complex bases (or operands) consisting of (a) a root and other affixes, (b) multiple roots, or (c) multiple roots and other affixes. Examples of these follow:

• undo (consisting of prefix un- and root do)
• untouchable (consisting of prefix un-, root touch, and suffix -able)
• non-childproof (consisting of prefix non-, root child, and root proof)
• non-childproofable (consisting of prefix non-, root child, root proof, and suffix -able)

English words may consist of multiple prefixes: anti-pseudo-classicism (containing both an anti- prefix and a pseudo- prefix).

Prefix	Meaning	Example
A-	verb > predicative adjective with progressive aspect	afloat, atremble
Be-	equipped with, covered with, beset with (pejorative or facetious)	bedeviled, becalm, bedazzle, bewitch
Co-	joint, with, accompanying, together	co-worker, coordinator, cooperation
Counter-	against, in opposition to	counteract, counterpart, counterterrorism
Down-	to make something lesser, lower or worse	downgrade
En-/em-	to make into, to put into, to get into	enmesh, empower
Ex-	former	ex-husband, ex-boss, ex-colleague
for-	without	forbid, forget, forgo
fore-	before	forearm, forerunner, foretell
Mid-	middle	midlife
Midi-	medium-sized	midi-length
Mini-	small	minimarket, mini-room
Mis-	wrong, astray	misinformation, misguide
Out-	better, faster, longer, beyond	outlive, outreach
Over-	too much	overreact, overact
Re-	again, back	rerun
Self-	self	self-sufficient
Step-	family relation by remarriage	stepbrother
Twi-	two	twibill, twilight
Un-	not, opposite of	unnecessary, unequal
Un-	reverse action, deprive of, release from	undo, untie
Under-	below, beneath, lower in grade/dignity, lesser, insufficient	underachieve, underground, underpass
up-	to make something greater, higher, or better	upgrade
with-	against	withhold, withstand
ab-, a, abs-	away from	abduct, abnormal
Afro-	relating to Africa	Afro-American
ambi-	both	ambitendency
amphi-	two, both, on both sides	amphiaster, amphitheater, amphibian
an-, a-	not, without	anemic, asymmetric
ana-/an-	up, against	anacardiaceous, anode
Anglo-	relating to England	Anglo-Norman
ante-	before	antebellum, antediluvian, antenatal
Anti-	opposite	anti-clockwise
Anti-	against	anti-war, anti-virus, anti-human
Apo-	away from	apomorphine
Arch-	supreme, highest, worst	arch-rival, archangel
Astro-	star	astrobiology
Auto-	self	autobiography, automatic
Bi-	two	bicycle
Bio-	biological	biodegrade
Circum-	around	circumnavigate
Cis-	on this side of	cislunar
Con-, co-, col-, com-, cor-	together or with	confederation, commingle, colleague, correlation, cohabit
Contra-	opposite	contradict
Cryo-	ice	cryogenics
Crypto-	hidden, secret	cryptography
De-	down	depress
De-	reverse action, get rid of	de-emphasise
Demi-	half	demigod
Demo-	people	demography
Di-	two	dioxide
dia-	across, through	diameter
dis-	not, opposite of	disloyal, disagree
Dis-	reverse action, get rid of	disconnect, disinformation
Dis-, di-, dif-	apart	differ, dissect
Du-, duo-	two	duet
Eco-	ecological	ecosystem
Electro-	electric, electricity	electro-analysis
Epi-	upon, at, close upon, in addition	epidermis
Euro-	European	Eurocentric
Ex-, e-, ef-	out of	export
Extra-	outside	extracurricular
Fin-	kinship	affinity
Franco-	French, France	Francophile
Geo-	relating to the earth or its surface	geography
Hetero-	different	heterosexual
Hemi-	half	hemimorphic
Homo-	same	homosexual
Hydro-	relating to water, or using water	hydroelectricity
Hyper-	above, over	hyperthermia
Hypo-	under or below something, low	hypothermia
Ideo-	image, idea	ideograph
Idio-	individual, personal, unique	idiolect
In-	in, into	insert
In-/il-/im-/ir-	not, opposite of	inexact, irregular
Indo-	relating to the Indian subcontinent	Indo-European
Infra-	below, beneath	infrared
Inter-	among, between	intercede
Inter-, intel-	between, among	interact, interstate
Intra-	inside, within	intravenous
Iso-	equal	isochromatic
Macr(o)-	long	macrobiotic
mal-	bad, badly	malnourish
Maxi-	very long, very large	maxi-skirt
medi-	middle	medieval
Mega-, megalo-	great, large	megastar, megalopolis
Meta-	after, along with, beyond, among, behind	meta-theory
Micro-	small	microbacillus
Mon(o)-	sole, only	monogamy
Multi-	many	multi-storey
Neo-	new	neolithic
Non-	not	nonexistent
Octo-	eight	octagon
Omni-	all	omnipotent, omnipresent
Paleo-	old	paleolithic
Pan-	all, worldwide	pan-African
Para-	beside, beyond	parallel
Ped-/pod-	foot	pedestrian, podiatrist
per-	through, completely, wrongly, exceedingly	permeate, permute
peri-	around	perimeter, periphrase
Photo-	light, photography, photograph	photoelectric
poly-	many	polygon
Post-	after	postpone, post-election, post-graduation
pre-	before	predict
Preter-	beyond, past, more than	preternatural
Pro-	substitute, deputy	proconsul
Pro-	for, on the side of	pro-life
Pro-	before	procambium
Pros-	toward	prosthesis
Proto-	first, original	protoplasm, prototype
pseudo-	false, imitation	pseudonym
pyro-	fire	pyrokinetic
quasi-	partly, almost, appearing to be but not really	quasi-religious
retro-	backwards	retrograde
semi-	half	semicircle
soci-	society, social, sociological	sociopath
sub-, su-, suc-, suf-, sug-, sum-, sup-, sur-, sus-	below, under	submerge, success, support, surreptitious, suspect, sustain
super-	above, over	supervisor
supra-	above, over	suprarenal
sur-	above, over	surname, surreal, surrender
syn-, sy-, syl-, sym-, sys-	together, with	synthesis, symbol, syllable, system
tele-	at a distance	television
trans-	across	transatlantic, transverse
tri-	three	tricycle
ultra-	beyond	ultramagnetic, ultraviolet
uni-	one	unicycle
vice-	deputy	vice-president, vice-principal