The hyphen is for punctuating words, either for joining or separating them. Hyphens form compound words, connect prefixes to words, or create linked adjectives. Using hyphens to separate words is only necessary when formatting justified text for readability. So we’ll only look at hyphens as linkers.
Unlike the rules for using periods, the rules for hyphens are fluid. As such, most recommendations are based on what produces a readable sentence. Different style guides will recommend similar and different ways to use the hyphen, so the best way to know whether a word needs a hyphen is to consult an up‐to‐date dictionary (differences exist among British, Australian, and American dictionaries).
But sometimes the dictionary won’t provide the answer you need. For example, ‘up‐to‐date’ is in the New Oxford American Dictionary. But the unhyphenated form—‘up to date’—is also listed. So, how do you know which to use? How did I know to use the hyphenated form in the previous paragraph?
Test for Hyphen Usage
- If you can’t reverse the order, use a hyphen.
- If you can’t remove one of the words, use a hyphen.
‘Up‐to‐date’ met both of these criteria. It would sound strange, or can mean something else entirely, if a word were removed, e.g. ‘up to dictionary’ or ‘up date dictionary.’ Also changing the order of the words (to‐date‐up) causes a readability problem. Ergo, hyphenate ‘up‐to‐date.’
COMMON WAYS TO USE A HYPHEN
I. Use to join words that together are a single unit of meaning
This is the most common way to use a hyphen. When a group of words modifies a noun, link them together with hyphens. The test above applies to this usage.
II. Suspended Hyphens
When more than one item modifies a noun, and you want to be concise, suspended hyphens save the day.
“nineteenth‐ and twentieth‐century political movements”
“single‐ or multiple‐blank sentences”
III. With compound Object-Verbal Noun
Sometimes an object and a verb need to be linked with a hyphen to avoid misreading and confusion:
“man eating shark”
means that a person is consuming a shark. Whereas:
means that a shark likes the taste of human flesh.
IV. Use with some prefixes and suffix
More often than not, use a hyphen with the following prefixes and suffix: all-, ex-, self-, half-, quasi-, or -elect.
V. Use when a prefix is attached to a proper noun
When you place a prefix on a proper noun, it is best to use a hyphen. Again, this ensures that no one misreads what you have written.
VI. Use with fractions and compound numbers
Maybe the second-most popular usage, numbers and fractions need a hyphen.
“twenty-nine years old”
“two-thirds of ice cream cones”