Hyphens are like children – short and troublesome. There are a few important rules for using hyphens, but British and American dictionaries approach them differently. This can lead to confusion.

The best approach is to follow the practice of one dictionary. The Style manual for authors, editors and printers, sixth edition, (available at Monash libraries) has seven pages on the use of hyphens, and is the best place to learn all the rules. If you only need to check if a particular word or phrase should be hyphenated, use the Macquarie Dictionary.

A hyphen joins two words, or a prefix and a word, or a word and a suffix. Hyphens are an important tool to avoiding ambiguity, but you don’t need to overuse them. When deciding on whether to use a hyphen, consider the context in which a word or words appear.

Remember to distinguish between hyphens and dashes. Dashes are longer than hyphens and, in general, hyphens join and dashes separate.

When it comes to hyphens, the best rule is to look the potentially hyphenated word up. However, here are a few rules that may help with hyphen use.

Use a hyphen for compound adjectives

  • a five-year-old child (but: The child was five years old.)
  • a university-owned centre

Use a hyphen with some prefixes to avoid double vowels
Generally, if a prefix ending in a vowel is paired with a noun beginning with the same vowel, you need to add a hyphen.

  • pre-eminent

However, words that are firmly entrenched in the lexicon are often exceptions.

  • coordinate

Use a hyphen if not using a hyphen would make the meaning unclear
Always look for possible ambiguities.

  • a small molecule-interaction laboratory
  • a small-molecule interaction laboratory