A phrasal adjective (also known as an adjective phrase or compound adjective) is a phrase that modifies a noun.
Phrasal adjectives preceding nouns
When a phrasal adjective precedes a noun, it takes a hyphen or, for phrases of three or more words, hyphens. This makes things easier for your reader and helps prevent miscues—for example:
. . . scary-sounding bus accident . . . [New York Magazine]
. . . razor-sharp wit and over-the-top characters to create a twang-tinged, toe-tapping twist . . . [IDS News]
The larger-than-life personality of Welles, a Kenosha native, is well captured in this nimble period piece and coming-of-age story . . . [JS Online]
We make exceptions for phrasal adjectives beginning with -ly adverbs—for example:
poorly run bank
closely held positions
Such phrases are conventionally unhyphenated.
Phrasal adjective hyphenation
When two closely related phrasal adjectives have similar ending elements, remove the ending element from the first phrase and leave the hyphen, like so:
the four- or five-year-old girl
Most phrasal adjectives that follow their nouns are left unhyphenated. But there are a few phrases that are conventionally hyphenated no matter where they fall in a sentence—for example:
That would be ill-advised.
There are many who think e-mail is old-fashioned . . .
When in doubt about whether to hyphenate a phrase like these, check a good dictionary. Most phrases that are always hyphenated will be so listed.
Phrasal adjectives and units
When a phrasal adjective denotes an amount, a number, or a duration, the unit is singular—for example:
the four-story, 50-unit complex
65.5-million-dollar projection
