Compound adjectives

English is a very creative language in the sense that new words are invented every day, and one easy way to create a new term is to make compound nouns or adjectives. Thus, an animal with cold blood is a cold-blooded animal. Cold-blooded is a compound adjective made up of an adjective and a noun, to which the suffix-ed has been added. This word ending in -ed may look like a participle but in fact it is not, because in order to be a participle, the root has to be a verb, not a noun.
A few more examples:
A man with dark hair and blue eyes is a dark-haired, blue-eyed man.
A person with long legs is a long-legged person.
As you can see, all these examples are formed by adding -ed to an adjective-noun combination. But this is by no means the only one possible. Keep reading to find others.

Frogs are cold-blooded animals
Image by Drriss

A compound adjective is a combination of two or more words that works as an adjective. These words can be adjectives, nouns, adverbs or participles, and they can be hyphenated or not. A hyphen is a punctuation mark in the form of a short line (-) that is put between two words to join them.

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These compounds can be written as one word (waterproof), two separate words (brick red) or they can be hyphenated (snow-white). The compounds that are used more often tend to appear in one word. Those that combine occasionally but keep their individual meaning tend to use a hyphen. And those that come in two words keep their independent identity. But British and American English don't always use the hyphens in the same word combinations, so, when in doubt, check a good dictionary!

Sometimes, more than two words can be found forming a compound (up-to-date, state-of-the-art,..) These expressions are only found hyphenated when they precede the noun they qualify, but not when they follow linking verbs. Examples:
If you are a fashion lover, read these tips to stay up to date.
I like to follow the latest up-to-date trends.
His house is state of the art. It is full of the latest gadgets.
I love state-of-the-art technology.

State-of-the-art technology
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Let's have a look at the different combinations that we can find:
Noun + adjective
Trustworthy, blameworthy, duty-free, tax-free, seasick, watertight, waterproof, colour-blind, worldwide, knee-deep, self-conscious, and other compounds that are equivalent to the construction "as...as..." : brick red (as red as brick), stone-cold (as cold as a stone), paper-thin (as thin as paper)
Adjective+adjective

• A combination of two qualities: bitter-sweet, deaf-mute.
• A combination in which the first element takes the suffix -o: socio-economic, Anglo-Saxon, Franco-German, Anglo-American. In this case, all the combinations are hyphenated.
• A combination in which the first adjective qualifies the second adjective: dark-blue, red-hot, Roman-Catholic.

Adverb+adjective
Evergreen, oversensitive, all-American
Noun+present participle
Self-defeating, self-denying, heart-breaking, breath-taking, law-abiding, 
Noun+past participle
Self-taught, hand-made, thunderstruck, home-brewed, heart-felt, brightly-lit, open-minded, well-behaved
Adjective or adverb+present participle
Forthcoming, everlasting, neverending, easygoing, good-looking
Adjective or adverb+past participle
Far-fetched, well-meant, widespread, new-laid, long-awaited
Number+ noun
Second-hand, first-rate. Notice that adjectives using numbers, like any other adjectives, are not found in the plural. Thus, a boy who is twelve years old is a twelve-year-old boy, or a tree which measures three metres is a three-metre-tall tree. These expressions with numbers are always hyphenated.
Adjective+ noun
Apart from the common formation that we have seen at the beginning of this post, in which the noun takes the suffix -ed, there are other possibilities such as last-minute, deep-sea, ...
Noun+noun
Part-time
Verb+adjective or adverb
Feel-good, buy-now, pay-later

And remember that new combinations are always possible. You can create your own adjective!

Let's watch this video about two beautiful brown-eyed girls. Notice that the song by Van Morrison is called "Brown Eyed girl". Why doesn't it have a hyphen? Because you don't need it in titles! Enjoy!

Exercises:
Choose the correct  adjective from the ones given
Complete the sentences with a compound adjective
Choose the appropriate compound adjective
For advanced students
Match the compound adjectives with their definitions