What is a hyphen?
- A hyphen (-) is a punctuation mark that’s used to join words or parts of words. It’s not interchangeable with the various dashes.
- Hyphens are often used in compound modifiers when the modifier comes before the word it’s modifying.
- If you’re not sure whether a compound word has a hyphen, check your preferred dictionary.
Hyphens with compound modifiers: Multiple-word adjectives before nouns
Using hyphens to connect words is easy. Picking the right words to connect is a little harder. Let’s start with compound modifiers, also known as phrasal adjectives.
A compound modifier is made up of two or more words that work together to function like one adjective in describing a noun. When you connect words with a hyphen, you make it clear to readers that the words work together as a unit of meaning.
It would be easy to read the above sentence as saying that you shouldn’t take down any load that is holding up a wall. A hyphen should be inserted between load and bearing to make it clear that we’re talking about walls that are bearing a load.
Generally, you need the hyphen only if the two or more words are functioning together as an adjective before the noun they’re describing. If the noun comes first, we usually leave the hyphen out.
You never use a hyphen when your modifier is made up of an adverb ending in -ly and an adjective.
Hyphens and compound modifiers with participles
Compound modifiers that include present or past participles follow the same rules as any other compound modifier.
Hyphens in compound modifiers with present participles
When we combine an adjective, a noun, or an adverb that doesn’t end in -ly with a present participle (the –ing form of a verb) to describe another word, we use a hyphen to make the meaning of the combined descriptor clear.
Without the hyphen between beautiful and looking, your reader may stumble over the sentence. Perhaps there’s a new type of daisy called the “looking flower”?
Don’t use a hyphen when the modifier comes after the noun it’s describing.
Don’t use a hyphen when you are combining an adverb ending in -ly and a participle.
Hyphens in compound modifiers with past participles
Compound modifiers that contain a past participle follow the same rules as other compound modifiers. Use a hyphen when the compound goes before the noun it modifies:
Don’t use a hyphen when the compound comes after the noun it describes.
Hyphens with high and low
When using high or low as part of a compound modifier, use a hyphen when the compound comes before the noun it’s modifying.
Hyphens and compound words
Hyphenated compound words are multi-word terms with a hyphen or hyphens between their component words. Over time, many hyphenated compounds become closed compounds—teen-ager became teenager, for instance. Check a dictionary if you’re not sure how to treat a compound. Here are a few examples of common hyphenated compound words:
Closed compound words
Hyphenated words tend to become closed compounds (single words, with no spaces and no hyphens) over time. Email instead of e-mail, for example, is increasingly common. If you aren’t sure whether a word is a closed compound or a hyphenated one, check your preferred dictionary.
Open compound words
Open compounds are typically made up of two nouns that are used together to represent a single idea. “Open” means that there is a space between the two words and no hyphen. Again, a good dictionary is the best place to find out how to treat compounds—if the compound isn’t in the dictionary, that means it should be open.
Hyphens and numbers
Numbers between twenty-one and ninety-nine should be hyphenated when they’re spelled out.
Spelled-out two-word simple fractions are also hyphenated. One-word simple fractions (such as half and quarter) as part of a compound are not joined by hyphens to the other word or words of the compound in its noun form, however.
Hyphens in compound modifiers involving numbers
When a number appears as the first part of a compound modifier that comes before a noun in a sentence, the compound modifier is hyphenated. This applies whether the number is spelled out or in numerals, and whether it is cardinal or ordinal.
However, a hyphen is not required if the number is the second word in the compound adjective.
Hyphens are also not used between a number and the word percent appearing before a noun.
Hyphens in compound modifiers involving fractions
When a fraction (e.g., half or quarter) is used as part of a compound adjective appearing before a noun, it should be hyphenated.
The word half also combines with other words to form compounds in nonmathematical contexts. These compounds are generally hyphenated when they are used as adjectives (before or after a noun) and open when they are used as nouns or verbs.
Hyphens with prefixes: Ex-, self-, all-
Use a hyphen with the reflexive prefix self-.
When using all as part of a compound, use a hyphen if the compound is adjectival and leave the compound open if it is adverbial.