In linguistics, 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 English parts of speech, although historically they were classed together with the nouns. Certain words that were traditionally considered to be adjectives, including the, this, my, etc., are today usually classed separately, as determiners.

Types of use
A given occurrence of an adjective can generally be classified into one of three kinds of use:

·      Attributive adjectives are part of the noun phrase headed by the noun they modify; for example, happy is an attributive adjective in "happy people". In some languages, attributive adjectives precede their nouns; in others, they follow their nouns; and in yet others, it depends on the adjective, or on the exact relationship of the adjective to the noun. In English, attributive adjectives usually precede their nouns in simple phrases, but often follow their nouns when the adjective is modified or qualified by a phrase acting as an adverb. For example: "I saw three happy kids", and "I saw three kids happy enough to jump up and down with glee."

·      Predicative adjectives are linked via a copula or other linking mechanism to the noun or pronoun they modify; for example, happy is a predicate adjective in "they are happy" and in "that made me happy."

·  Nominal adjectives act almost as nouns. One way this can happen is if a noun is elided and an attributive adjective is left behind. In the sentence, "I read two books to them; he preferred the sad book, but she preferred the happy", happy is a nominal adjective, short for "happy one" or "happy book". Another way this can happen is in phrases like "out with the old, in with the new", where "the old" means, "that which is old" or "all that is old", and similarly with "the new". In such cases, the adjective functions either as a mass noun (as in the preceding example) or as a plural count noun, as in "The meek shall inherit the Earth", where "the meek" means "those who are meek" or "all who are meek".

Distribution
Adjectives feature as a part of speech (word class) in most, but not all, languages. In some languages, the words that serve the semantic function of adjectives may be categorized together with some other class, such as nouns or verbs. For example, rather than an adjective meaning "big", a language might have a verb that means "to be big", and could then use an attributive verb construction analogous to "big-being house" to express what English expresses as "big house". Such an analysis is possible for the Chinese languages, for example.

Different languages do not always use adjectives in exactly the same situations. For example, where English uses to be hungry (hungry being an adjective), Dutch and French use honger hebben and avoir faim respectively (literally "to have hunger", the words for "hunger" being nouns). Similarly, where Hebrew uses the adjective זקוק zaqūq (roughly "in need of"), English uses the verb "to need".

In languages which have adjectives as a word class, they are usually an open class; that is, it is relatively common for new adjectives to be formed via such processes as derivation. However, Bantu languages are well known for having only a small closed class of adjectives, and new adjectives are not easily derived. Similarly, native Japanese adjectives (i-adjectives) are considered a closed class (as are native verbs), although nouns (an open class) may be used in the genitive to convey some adjectival meanings, and there is also the separate open class of adjectival nouns (na-adjectives).

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