Hyphenating prefixes correctly is not easy. There are some rules and some personal choices.
Use a hyphen with these prefixes:
- all-
- cross-
- ex-
- self-
- co-
- semi-
- anti-
As in these examples:
- all-conquering team
- cross-country runner
- ex-girlfriend
- self-service
- co-owner
- semi-circular
- anti-aircraft gun
Hyphens are used before a proper noun.
- trans-Siberian train
- un-English
Hyphens are used before a number.
- mid-1990s
- pre-20th century
Hyphens are used before an abbreviation.
- non-ISO compliant
- pre-COVID-19
Hyphens are used when the prefix ends with the same vowel that the base word being connected to it begins with.
- re-enter
- ultra-aggressive
Hyphens are used to make the meaning of the word clear.
- Co-op
(The short form of co-operate.)
Coop
(A place to keep chickens.) - Re-sign
(To sign again.)
Resign
(To leave your job.) - Man eating shark.
(A man is eating a shark.)
Man-eating shark.
(A shark that eats people.) - She has a concealed gun licence.
(You her cannot see her gun licence.)
She has a concealed-gun licence.
(She has a licence to carry concealed guns.)
If the word is easy to read without a hyphen, don’t use one. If it is difficult to read put one in. These examples show when personal choice can be used.
- The story is set in prewar England.
The story is set in pre-war England. - Should I restart the car.
Should I re-start the car. - The soldiers were using their new infrared glasses.
The soldiers were using their new infra-red glasses.
Your choice.
