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:
Tip: 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 (e.g. high-quality wine, the wine is high quality).
Follow the modifier rule for hyphenating most combinations, including:
- adjective + noun
- adjective + participle
- noun + noun
If the 2 nouns are equal in weight (rather than the first noun modifying the second), use an en dash rather than a hyphen
- noun + participle
- participle + noun
- noun + gerund
- gerund + noun
- phrase that acts as an adjective
- adverb not ending in -ly + participle or adjective (see Exceptions to the modifier rule for adverbs ending in -ly + participle or adjective)
- 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
- superlatives with ordinal numbers
- participle + preposition
- participle + adverb
- ranked (or ordinal) number + noun