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You can use a hyphen (or hyphens) to link the words in a compound adjective to show it is a single adjective. (A compound adjective is a single adjective that is made up of more than one word.) For example:
- two-seater aircraft
- never-to-be-forgotten experience
What Is a Compound Adjective?A single adjective made up of two or more words is called a compound adjective. The words in a compound adjective can be linked together by a hyphen (or hyphens) to show they are part of the same adjective.
In the UK, your readers will expect you to use hyphens in compound adjectives.
In the US, your readers will be more lenient. The US guidance is as follows:
Use a hyphen if it eliminates ambiguity or helps your reader. If you're unsure, use a hyphen.
The Hyphen Might Be EssentialSometimes, a hyphen is essential to avoid ambiguity. Look at these examples:
- a heavy-metal detector
- a heavy metal detector
Compound Adjectives with NumbersThe easiest compound adjectives to spot are the ones that include numbers. For example:
- Two-seater aircraft
- 4-bedroom house
"24-hour" (This is correct.)
"3-day" (This is correct.)
- Three stone weakling (Three-stone would be better.)
- 15-page document
Compound Adjectives Without NumbersLots of compound adjectives do not include numbers. For example:
- Philip is a far-too-chatty individual.
- That was a never-to-be-forgotten experience.
- James is a second rate plumber.
This should be should be "8-week money-back guarantee".
"Cambridge-based" and "high-speed" (both correct)
Often, a compound adjective consists of words that would not normally be joined together with a hyphen. For example:
- The double glazing is still leaking. Can you call that double-glazing salesman? (The words double glazing only need a hyphen when they are functioning as an adjective. In this example, the first time they are used, they are not an adjective. The second time they are used, they are an adjective describing salesman.)
- You call this silver service? She's not a trained silver-service waitress. (The second time they are used, the words silver service describe waitress. As they are a compound adjective, they are linked with a hyphen to show they are a single adjective.)
What Is an Adjective?An adjective is a describing word (e.g., red, big, beautiful, contagious).
Read more about adjectives.
What Is a Compound Adjective?A single adjective made up of two or more words is called a compound adjective. The words in a compound adjective are often linked together by a hyphen (or hyphens) to show that they are part of the same adjective. For example (compound adjectives shaded):
- three-page document
- ironing-board cover
More Than One Adjective or a Compound Adjective?Do not be tempted to string all adjectives together with hyphens. It is common to use more than one adjective to describe something. When you use 2 or more adjectives to describe one thing, it is called enumeration of adjectives. For example:
- A big maroon car (Here, big and maroon are standalone adjectives. This is an example of enumeration of adjectives. There is no compound adjective.)
- She is an intelligent articulate lady. (Here, intelligent and articulate are standalone adjectives. This is an example of enumeration of adjectives. There is no compound adjective.)
Adverbs with AdjectivesAdjectives are often preceded by adverbs (e.g., very, well, beautifully, extremely).
Usually, there is no need to link an adverb to an adjective using a hyphen. For example:
- Young Paula is a very talented student. (As very is an adverb, it should not be linked to the adjective talented with a hyphen.)
- It is a wonderfully-decorated tree. (The adverb wonderfully modifies the adjective decorated, but there is no need to join the two with a hyphen.)
- Alan is the best-known player on the pitch. (In this example, Alan is known better than any other player.)
- Alan is the best known player on the pitch. (This example could be taken to mean the same as the one above or it could be taken to mean that Alan is the best player of all the known players on the pitch. The hyphen eliminates ambiguity.)
How To Spot a Compound AdjectivePut and between the adjectives. If there is no loss of meaning, then you are very likely dealing with several adjectives as opposed to a compound adjective. Let's try it:
step 1 large proud rooster
step 2 large and proud rooster
Although different in style, there is no loss of meaning. This is an example of two adjectives. Therefore, no hyphen is required.
step 1 free range rooster
step 2 free and range rooster
In this example, there is a change in meaning. The rooster is not free and what is a range rooster? This is a compound adjective and should be written as free-range rooster.
step 1 first aid post
step 2 first and aid post
Although aid post is okay, there is a change in meaning with first post. This should be written as first-aid post.