Compound Adjectives: To Hyphenate or not?

What are compound adjectives?

These are adjectives which are made up of more than one word, and there are many possible combinations.

Examples:

• adjective + noun: last-minute, shoulder-length
• noun + adjective: lead-free, goal-hungry

Very often, a -d or -ed is added to a noun to make it a past-participle construction.

• adjective + past participle: loud-mouthed, red-haired
 
• adjective/noun/adverb + present participle: evil-looking, awe-inspiring, never-ending
• number + noun: twenty-dollar, ten-kilometre

Whether these adjectives should be hyphenated or not is a difficult decision. The best advice would be to consult a good dictionary.

Generally, if there isn't any risk of ambiguity, or the compound adjective is a common one, hyphens aren't necessary.

Consider these:

He's just gone out for an early-morning run.
He's just gone out for an early morning run.

Both mean the same.

Brad is a Chinese martial arts practitioner.
Brad is a Chinese-martial-arts practitioner.

Is Brad Chinese or isn't he? Does he practise Chinese, Japanese or Indonesian martial arts?

However, there are certain compound adjectives that are always hyphenated, unless they can be written as one word.

• Numbers: fifty-dollar bill, one-man show, thirty-five-year-old woman, 21st-century technology
• Present participle construction (see above): good-looking actor, deeply-boring lesson
• Past participle construction (see above): tongue-tied child, old-aged pensioners
• Colours: yellowish-blue skirt, light-purple top
• Comparatives and superlatives: highest-ever inflation, lower-paid sector

These are general guidelines. When in doubt, consult a dictionary, or ask in Twitter with the hashtag #grammar. Be sure to follow me!