In grammar, an adjective is a 'describing' word; the main syntactic role of which is to qualify a noun or noun phrase, giving more information about the object signified.

Adjectives are one of the traditional eight English parts of speech, though linguists today distinguish adjectives from words such as determiners that were formerly considered to be adjectives. In this paragraph, "traditional" is an adjective, and in the preceding paragraph, "main" and "more" are.

Most but not all languages have adjectives. Those that do not typically use words of another part of speech, often verbs, to serve the same semantic function; for example, such a language might have a verb that means "to be big", and would use as attributive verb construction analogous to "big-being house" to express what English expresses as "big house". Even in languages that do have adjectives, one language's adjective might not be another's; for example, whereas English uses "to be hungry" (hungry being an adjective), Dutch and French use "honger hebben" and "avoir faim," respectively (literally "to have hunger", hunger being a noun), and whereas Hebrew uses the adjective "זקוק" (zaqūq, roughly "in need of"), English uses the verb "to need".