adjective, English part of speech, one of the two that refer typically to attributes and together are called modifiers. The other kind of modifier is the adverb. Adjectives and adverbs are functionally distinct in that adjectives modify nouns and pronouns, while adverbs typically modify verbs. In English, comparative adjectives end in – er or are preceded by more (e.g., "She is happier,""She is more capable"); superlative adjectives end in – est or are preceded by most ("happiest,""most capable"). English adverbs typically end in – ly ("happily"). Adjective and adverb are Indo-European form classes; some non-Indo-European languages lack specialized classes with analogous functions.
See P. Roberts, Understanding Grammar (1954) and Modern Grammar (1968); E. Finegan and N. Besnier, Language: Its Structure and Use (1989).