“Hyphenation” is a term for linking two words with a hyphen to make a compound word. In this context, “compound” simply means two separate words have been joined together. But when should you hyphenate a word? We’ll explain the basics below.
Compound adjectives are formed by joining two words (e.g., “good-looking,” “power-hungry” or “accident-prone”). Further examples include:
Compound adjectives can be composed of more than two words, making them more like phrases:
Compound adjectives like these are often only be hyphenated if they appear before what they are describing in a sentence. For example, the compound adjective in “The well-known artist Whistler…” could also be used without a hyphen later in the sentence: e.g., “The artist Whistler was well known…”
However, some modifiers are hyphenated regardless of where they appear in a sentence, such as “error-free” (e.g., “the error-free paper” and “the paper was error-free” are both correct).
Compound Nouns and Verbs
It is more difficult to know when to hyphenate nouns and verbs. In many cases, it is simply a matter of convention (e.g., “mother-in-law”). The best thing to do with these terms is check a dictionary. If you find a term where the hyphen is optional, your main guideline should be consistency.
Many words that begin with the prefixes “non-,” “pre-,” “de-,” or “re-” are hyphenated, but this is only necessary when it prevents a letter clash.
For example, we hyphenate “re-evaluate” because “evaluate” starts with the same letter that precedes it. But we do not hyphenate “retry” because there is no letter clash. This isn’t always true, but it is a good rule of thumb (and you can always check a dictionary if you’re not sure about a word).
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A hanging or suspended hyphen can be used when two compound terms contain the same second element. For instance, a company might say “we offer five- and ten-year mortgages.” Here, the hyphen after “five” shows that we mean “five-year and ten-year mortgages” but didn’t want to repeat “year.”
This can also be done with closed compounds, such as in “under- and overground trains.” Note that we use a hyphen after “under” even though the full word would be “underground,” without a hyphen.
Hyphenating for Clarity
In some cases, we also use a hyphen to ensure clarity. Omitting a hyphen can even change the meaning of some sentences. For example:
I once saw a man-eating crocodile.
I once saw a man eating crocodile.
The first sentence here describes a crocodile as “man-eating” (i.e., a crocodile that eats humans). The second, non-hyphenated sentence describes a man eating crocodile meat.
Rules about which words should be hyphenated can vary between institutions, though, so be sure to double check your style guide.
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