compoundadjective

A compound adjective is an adjective formed from two or more words that function together as a single modifier before a noun. These compounds often combine an adjective with a noun, another adjective, or a participle to convey a more specific meaning than the base words alone. Common examples include well-known, high-speed, stone-faced, blue-green, old-fashioned, and two-story.

Compound adjectives are typically written with a hyphen when they precede the noun they modify, to signal that the words form one unit. For example, a well-known author, a high-speed pursuit, a blue-green color. When the compound adjective follows the noun, the hyphen is usually dropped and the phrase is not treated as a single modifier, as in the author is well known or the car was fast and reliable (predicate position). Some compounds may be written in closed form over time, such as online or downtown, though many attributive uses still prefer hyphenation.

Formation and variety: compounds can be of different kinds, including adjective+noun (blue-eyed), noun+participle (stone-faced), determiner+adjective+noun (two-year-old), or multiple adjectives (long-term, self-reliant). In many cases, the choice of hyphenation depends on clarity, style, and conventional usage. Adverbial elements ending in -ly are often not hyphenated when forming a compound adjective (widely known) in some styles, while others retain hyphenation in the same position (well-known).

Usage notes: a string of words must function as a single modifier, and it should appear before the noun it modifies. Not all multiword phrases qualify as compound adjectives; if the phrase does not modify a noun directly or is used predicatively, hyphenation may be unnecessary. Different style guides (AP, Chicago, MLA) provide varying rules on hyphenation and exceptions.