When we add prefixes to root words we sometimes need to use a hyphen (-).

If the prefix ends in a vowel and the root word begins with a vowel, a hyphen is often used.

de-ice

pre-order

A hyphen is also used if the root word is a proper noun or an adjective that needs a capital letter. In the example below, European has a capital letter because it is formed from the proper noun Europe.

mid-December

trans-European

The prefixes all-, cross- and self- always have a hyphen.

all-powerful

cross-channel

self-aware

The prefix ex- always has a hyphen when it means former, or before.

ex-president

ex-husband

However, when the prefix ex- means going out, or getting bigger, it doesn't have a hyphen.

explode

expand

In this worksheet you can practise deciding whether or not to use a hyphen when adding prefixes to root words.