Building words with prefixes


We can change the meaning of a word by putting a little word called a prefix in front of the word.

Press the player above and listen to the podcast of this page and/or watch the video below and/or read on (or all!).

A lot of prefixes change the meaning of the word to the opposite meaning.

happy – unhappy,
legal – illegal,

like – dislike ,
patient – impatient, 
correct – incorrect.

Usually when you add a prefix you don’t change the root word.

multi + national = multinational
in + complete = incomplete

*notice the double letters in the following words. We just add the prefix to the root word *
dis + satisfied  = dissatisfied
mis + spell = misspell
un+ necessary = unnecessary
im + mature = immature
ir + responsible = irresponsible

There are hundreds of prefixes, some of the most popular are:

in-, ir-, il-, im-, un-, dis-, pre-, ex-, anti-, uni-, bi-

Recognising and understanding prefixes will help your spelling and reading.

There are some rules which help us to know which prefix to add to which word but like all rules there are exceptions.

* use il- before words starting with l    legible – illegible, illuminate, illegal, illegible
(But – unlawful, unlearn, unless…)

*use ir- before words starting with r     relevant – irrelevant, irresistible, irresponsible, irreconcilable, irregular, irradiate (But – unreal, unrated)

*use im- before words stating with m,  p  and  mature – immature, immigrant, immortal, immoral, immaterial, immaculate,    perfect – imperfect, impossible, impair, improper, impartial    balance – imbalance (But we have unpack, unpick, unpaid… unmarked, unmarried, unmask)


Common prefixes with their meanings ( some mean different things with different words).

The four most common prefixes are un-, re-, in-,  dis
These make up 58% of all prefixes in English.

un, in, il, im, ir, dis, non – these make nouns, verbs, adjectives negative, not, opposite.
unfair, untidy, unable, uncover, unkind, unequal, uneven, unusual
incomplete, informal, incorrect, indecent, insecure, indirect, inaccurate, inefficient, incompetent
illegal, illegitimate, illogical, illiterate, illegible, illustrious, illuminate
immature, impatient
irregular, irrelevant, irreplaceable, irresistible, irresponsible, irrational, irreconcilable, irreparable
dishonest, dislike, disagree, disappear, disgrace, disloyal, disobey, distrust, disadvantage, dissatisfied
non-smoker, non-toxic

de, dis, un, re these indicate reversal of verb’s actions – reverse, back, again
defrost, debug, decrease, deport, degrade, delete, detached
disconnect, disinterested, disarm, disable
unwrap, undo, untie, unplug, undress, unpack
return, retell, regain, repaint, retry, redo, replay, reuse, regain, reword, rebuild, remodel…

over, under, sub, mis to indicate something is wrong or bad, under, lowly
oversleep, overpopulated ( = too much, excessive)
undervalued, undercooked (= not enough)
substandard, subspecies (= not enough, lowly)
misunderstand, miscalculate, misspell, mistreat, misuse, misbehave, mistake (= bad)

hyper, mega, super, ultra, micro, mini – to indicate size very big, very small, too much
hypermarket, hyperactive
megastore, megabyte
supermarket, supermodel
ultrasound, ultra-modern
microwave, microchip
miniskirt, minibus

mono, uni, bi, tri, multi, semi – to indicate number, frequency, shape
monorail, monologue, monologue, monopoly = (one)
universal, unisex, unicycle, unison, unique, universe = (one, same)
bilingual, bicycle, bifocals, biweekly, biannual = (two)
triangle, tripod, tricycle, trilogy, triple, trio, triplets = (three)
multinational, multicoloured/multicolored (AmE), multicultural, multivitamin, multiplex, multimedia, multipurpose, multi-storey/multistorey (see hyphens (-) below) = (many)
semicircle, semicolon, semiconscious, semifinal (or semi-final)= (half)

hyphens (-)
e-book or ebook, e-mail or email, multi-storey or multistorey, anticlockwise or anti-clockwise?

All these spellings are correct. Some dictionaries have just the hyphen spelling, some say both spellings are OK.

Hyphens come and go. When it’s a new word it usually starts with a hyphen so as not to confuse people then soon the hyphen is dropped (e-mail now email) – this has been going on for centuries!

  • British English uses hyphens more than American English
  • you must use an hyphen when the prefix comes before a capital letter, anti-British, pro-European, because a capital letter can’t appear inside a word proEuropean.
  • single letter prefixes – e-commerce, e-book, e-mail but this changes with time. Now we have email, ebook.
  • sometimes if there are two vowels together and causes confusion – co-operate, re-align.
  • if a word looks the same as another – re-cover (cover something again) not recover from an illness.
Now try this exercise


Add a prefix to the word to make the opposite meaning.

(Type in the whole word)

Now try these exercises

Go to Word Building with suffixes – part 1