Compound modifiers (including adjectives and adverbs)

A modifier is a word or phrase that provides additional information, or ‘modifies’, another word. A compound modifier is where 2 words are brought together to form a new combined modifier:

blue     faster [modifiers]

accident-prone     dust-filled     fast-flowing     warm-blooded [compound modifiers]

Modifiers are hyphenated differently depending on where they are placed in the sentence. One key rule will answer most of your modifier hyphenation questions:


The modifier rule
Use a hyphen in a compound modifier when the modifier comes before the word it modifies, but leave it open if it comes after the word it modifies (eg high-quality wine, the wine is high quality).

Follow the modifier rule for hyphenating most combinations, including:

  • adjective + noun
long-term plan     planning for the long term
  • adjective + participle
open-ended question     the question is open ended
  • noun + noun
fire-escape stairs     a fire escape

If the 2 nouns are equal in weight (rather than the first noun modifying the second), use an en dash rather than a hyphen

cost–benefit analysis     the city–state of Monaco     gas–liquid chromatography
  • noun + participle
a heart-rending film     the film was heart rending
  • participle + noun
cutting-edge research     research that is cutting edge
  • noun + gerund
play-acting children     children who are play acting
  • gerund + noun
washing-machine parts     a washing machine
  • phrase that acts as an adjective
out-of-date publication     the publication was out of date
the well-known writer     the writer who is well known 
  • comparative or superlative adverb + adverb not ending in -ly

more-advanced seedlings     some seedlings were more advanced

the most-skilled workers     the workers who were most skilled

These compounds are often left open if there is no possibility of ambiguity

the most efficient method
  • superlatives with ordinal numbers
second-fastest runner     she was the second fastest
  • participle + preposition
an often referred-to book     this book is often referred to
  • participle + adverb
dressed-up children     the children were dressed up
  • ranked (or ordinal) number + noun
third-floor office     office on the third floor

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