using hyphens in compound adjectives
 
Hyphens should be used to link the words in compound adjectives. (A compound adjective is a single adjective that is made up of more than one word, e.g., two-seater aircraft or never-to-be-forgotten experience.)
 


What's 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.

Americans are more lenient. The US ruling is: Use a hyphen if it eliminates ambiguity or helps your reader, else don't bother. If you're unsure, use hyphens. You won't be marked down for using hyphens.

The Hyphen Might Be Essential

Sometimes a hyphen is essential to avoid ambiguity. Look at these examples:

a heavy-metal detector
a heavy metal detector

Both are correct, but they mean different things. The first device detects heavy metals. The second detects metal, and it is heavy. If we're talking about a device that detects heavy metals, then putting heavy metal detector would be wrong in the UK and the US.

Compound Adjectives with Numbers

The easiest compound adjectives to spot are the ones which include numbers.

Examples:

Two-seater aircraft

4-bedroom house


"24-hour" (This is correct.)
(newspaper article)


"3-day" (This is correct)
(newspaper article)

Three stone weakling
(Three-stone would be better.)

15-page document

Link with Hyphens If It's One Adjective

Not all compound adjectives include numbers. Often, a compound adjective consists of words that would not normally be joined together with a hyphen.

Examples:

The double glazing is leaking. Can you call that double-glazing salesman?  
(double-glazing describes salesman)

You call this silver service? She's not a trained silver-service waitress.
(silver-service describes waitress)


should be "8-week money-back guarantee"
(newspaper advertisement)


"Cambridge-based" and "high-speed" (both correct)
(magazine article)


Carl is far too chatty. Philip is another far-too-chatty individual.
(far-too-chatty describes individual)

It's true! The board outside the cafe read, "All-day breakfast 0830-1030."
(All-day describes breakfast)

That was a never-to-be-forgotten experience.    

James is a second rate plumber.  
 
ADJECTIVE?

An adjective is a describing word (e.g., red, big, beautiful, contagious). (See lesson Adjectives.)

COMPOUND ADJECTIVE?

A single adjective made up of two or more words is called a compound adjective. The words in a compound adjective are linked together by a hyphen (or hyphens) to show that they are part of the same adjective.

three-page document (< three-page is a compound adjective)
ironing-board cover (< ironing-board is a compound adjective)
 
 
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. (This is covered in more detail in the lesson Comma in Lists.)

A big maroon car
(2 adjectives: "big" and "maroon")
She is an intelligent articulate lady.   
(2 adjectives: intelligent and articulate)

ADVERBS WITH ADJECTIVES

Adjectives are often preceded by adverbs like very, well, beautifully, extremely, etc. (See lesson Adverbs.) 
Usually, there is no need to link an adverb to an adjective using a hyphen. 

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.)

Linking an adverb like very, most or least to an adjective with a hyphen is an uncommon error. However, when an adverb ends in -ly (and lots do), some writers feel the urge to link it to the adjective with a hyphen – there is no need.

It was a wonderfully-decorated tree.  
(The adverb wonderfully modifies the adjective decorated, but there is no need to join the two with a hyphen.)

However, with words like well, fast and best (which are both adjectives and adverbs), a hyphen can be used to avoid ambiguity.

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.
(In this example, Alan could be the best player of all the known players on the pitch.)

(This is covered in the lesson Adjectives and the lesson Adverbs.)
 
 
HOW TO SPOT A COMPOUND ADJECTIVE

Put and between the adjectives. If there is no loss of meaning, then you are very likely to be dealing with several adjectives, as opposed to a compound adjective.

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; no hyphen 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
 

See also:

What are adjectives?
What are compound adjectives?
Alternatives to hyphens in compound adjectives
Hyphens in compound nouns
Hyphens in prefixes


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