A prefix is a letter or group of letters added to the beginning of a word to make a new word.
Often the new word is just written as one word, for example:
Sometimes, however, a hyphen (-) is used to join prefixes to words, for example:
In the above examples, the prefix ends with a vowel and the root word begins with a vowel, so using a hyphen makes the new word easier to read. Without the hyphen we would get deice and reenter, which look very strange!
Words beginning with the prefix co- can be written with or without prefixes. Both of the following are correct.
In this worksheet, you can practise adding prefixes to root words and deciding whether or not to use a hyphen.