Prefixes

A prefix is a group of letters that is added to the beginning of a word (known as the base word or stem word) to create another word.

Most prefixes are set solid with the base word:

aero-     aeroplane

electro-     electromagnet

meta-     metadata

pre-     preoperative    

after-     afterthought

en-     encode 

micro-     microorganism    

pro-     pronoun

ante-     antenatal

exo-     exoskeleton

mid-     midterm    

pseudo-     pseudofluid

anti-     antibody

extra-     extramarital

milli-     millimetre

re-     readmit    

astro-     astronaut

geo-     geographic

mini-     miniskirt     

semi-     semidetached     

auto-     autosuggestion

hemi-     hemisphere

multi-     multitalented

stereo-     stereophonic

bi-     bipolar

hyper-     hyperactive     

nano-     nanoparticle   

sub-     subsystem    

bio-     biodata

hypo-     hypoglycaemic

non-     nongovernment    

super-     supermarket    

centi-     centipede

in-     inflexible

para-     paramilitary    

supra-     supraorbital

chemo-     chemotherapy

infra-     infrared

photo-     photograph

trans-     transgender    

co-     cochair

inter-     interdisciplinary

physio-     physiotherapy

tri-     trilateral    

counter-     counterterrorism

intra-     intravenous

phyto-     phytoactive

ultra-     ultrasound   

di-     diode

iso-     isotope

poly-     polyunsaturated    

un-     unflagging    

dis-     disinherit

macro-     macroeconomics

post-     postnatal

under-     underestimate

When the base term consists of more than 1 word, use an en dash after the prefix instead of a hyphen (see En dash):

the post–French Revolution period     pro–women’s rights

However, if the base term itself has a hyphen, use a hyphen after the prefix:

non-English-speaking people   not   non–English speaking people

Exceptions for hyphens with prefixes

Use a hyphen after the prefix when:

  • the word formed would otherwise be confused with another word
pre-fix/prefix     re-cover/recover     re-mark/remark     un-ionised/unionised
  • the combination of the prefix and the base word would create an unacceptable double or triple vowel in the middle of the word

ultra-aerated   not   ultraaerated

anti-aircraft   not   antiaircraft

  • the boundary between 2 parts of the word would otherwise be obscured

sea-legs   not   sealegs

non-event   not   nonevent

  • the base word begins with a capital letter or is a number
mid-1990s     non-Indigenous     post-2010     trans-Atlantic     un-Australian   
  • the prefix is e- (short for electronic), except for more established forms
e-book     e-health     e-learning   but   email
  • the prefix is ex- (meaning former)
ex-boyfriend     ex-student     ex-wife    
  • the prefix or first part of the word is cross, except for more established forms
cross-reference     cross-section     cross-country   but   crossover     crossbreed
  • the prefix or first part of the word is self-
self-conscious     self-awareness     self-destructive   but   selfless     unselfconscious

Did you know? Cooperate and coordinate started out with hyphens (co-operate, co-ordinate), to indicate that the 2 o’s did not form a double o.

These are now so familiar that confusion is unlikely, so they are set solid.

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