Prefixes

Prefixes are letters which we add to the beginning of a word to make a new word with a different meaning. Prefixes can, for example, create a new word opposite in meaning to the word the prefix is attached to. They can also make a word negative or express relations of time, place or manner. Here are some examples:

base word

prefixed word

type of meaning

possible

impossible

opposite

able

unable

opposite/negation

payment

non-payment

negation

war

pre-war

time (before)

terrestrial

extraterrestrial

place (outside of/beyond)

cook

overcook

manner (too much)

I’m sorry I was unable to attend the meeting.

Non-payment of fees could result in a student being asked to leave the course.

Has anyone ever really met an extraterrestrial being? (meaning a being from another planet)

The meat was overcooked and quite tasteless.

prefix

meaning

examples

anti-

against/opposed to

anti-government, anti-racist, anti-war

auto-

self

autobiography, automobile

de-

reverse or change

de-classify, decontaminate, demotivate

dis-

reverse or remove

disagree, displeasure, disqualify

down-

reduce or lower

downgrade, downhearted

extra-

beyond

extraordinary, extraterrestrial

hyper-

extreme

hyperactive, hypertension

il-, im-, in-, ir-

not

illegal, impossible, insecure, irregular

inter-

between

interactive, international

mega-

very big, important

megabyte, mega-deal, megaton

mid-

middle

midday, midnight, mid-October

mis-

incorrectly, badly

misaligned, mislead, misspelt

non-

not

non-payment, non-smoking

over-

too much

overcook, overcharge, overrate

out-

go beyond

outdo, out-perform, outrun

post-

after

post-election, post-war

pre-

before

prehistoric, pre-war

pro-

in favour of

pro-communist, pro-democracy

re-

again

reconsider, redo, rewrite

semi-

half

semicircle, semi-retired

sub-

under, below

submarine, sub-Saharan

super-

above, beyond

super-hero, supermodel

tele-

at a distance

television, telepathic

trans-

across

transatlantic, transfer

ultra-

extremely

ultra-compact, ultrasound

un-

remove, reverse, not

undo, unpack, unhappy

under-

less than, beneath

undercook, underestimate

up-

make or move higher

upgrade, uphill

There are no absolute rules for when to use a hyphen or when to write a prefixed word as one whole word (see the examples in the table). A good learner’s dictionary will tell you how to write a prefixed word.