Prefixes often used

Prefixes (at the beginning of words) can help you to understand what a new word means. Here are some common prefixes.

un- and dis-

These prefixes have two meanings: they can have a negative meaning (as above), but they can also mean ‘the opposite of an action’ or ‘to reverse an action’. This meaning is used with certain verbs.

• I locked the door when I left, but I lost the key, so I couldn’t it unlock it when I got back.
• I had to pack my suitcase (= put everything in it) very quickly, so when I unpacked (= took everything out) at the hotel, most of my clothes looked terrible.
• The plane appeared in the sky, then suddenly disappeared behind a cloud.
• In the morning you get dressed (= put on your clothes); when you go to bed you get undressed (= take off your clothes).

re- (= again)

• My homework was terrible, so I had to redo it.

• The shop closed down but will reopen next month.

• I failed my exam but I can retake (or redo/resit) it next year.

over- (= too much)

• I think my boss is overdoing it at the moment. (= working too hard; also overwork)

• I went to bed very late and I overslept (= slept too long) this morning.

• The shop assistant overcharged me. (= asked me for too much money)

mis- (= badly or incorrectly)

• I’m afraid I misunderstood what he said.
• Two of the students misread the first question.

Prefix	Meaning	Example
a	not	aseptic, asymmetrical
ab	away from	abnormal, absent
anti	against	antibiotic, antifreeze
auto	self, alone	automatic, automobile
bene	good	beneficial, benefit
bi	two, double	bicycle, bicentennial
bio	life	biology, biosphere
cent	hundred	century, centurion
centi	hundredth	centimeter
circum	around	circumference
co	with, together	cooperate
com	with	compassion, combine
con	with	connect
contra	against	contradict
deci	tenth	decimeter
deca	ten	decagon
dia	through	diagonal, diameter
dis	apart	dislocate, dismantle
eco	earth	ecology, ecosystem
equi	equal	equilateral, equilibrium
ex	former	ex-wife, ex-president
hemi	half	hemisphere
hyper	above, over	hyperactive
il/im	not	incorrect, irresistible
in/ir	not	incorrect, irresistible
inter	between, among	interstate, international
magni	great, large	magnify, magnificent
mega	great	mega city, megaphone
micro	small	microscope
mid	half	midway, middle
mini	very small	miniskirt
mis	wrong	misspell, misunderstand
mono	one, single	monotheistic, monologue
multi	many	multinational
non	not	nonconformist, nonentity
over	too much	overrun
pan	all	pan-American
para	beside, guard	parallel, parachute
penta	five	pentagon
per	throughout	perfect, pervade
poly	many	polygon
port	carry	portage
post	after	postpone, postgraduate
pre	before	prepare, predict
pro	forward, supporting	progress, propel, profess
quad	four	quadrilateral
re	again, back	reconsider
semi	half, partly	semidetached semiprivate
sub	below, under	submarine, submerge
super	above	superman, supernatural
tele	far	telephone, television
trans	across, over	transport, transplant
tri	three	triangle, tricycle
ultra	beyond	ultrasound, ultra light
un	not, uncertain	uneducated, unbearable
under	below	underused
uni	one	universal, unicycle