In linguistics, an adjective is a word that modifies a noun or noun phrase or describes its referent. Its semantic role is to change the information given by the noun. Traditionally, adjectives were considered one of the main parts of speech of the English language, although historically, they were classed together with nouns. Nowadays, certain words that usually had been classified as adjectives, including the this, my, etc., typically are classed separately as determiners.

English Grammar Terms III

In linguistics, the grammar of a natural language is its set of structural constraints on speakers 'or writers' composition of clauses, phrases, and words. The term can also refer to the study of such constraints, a field that includes domains such as phonology, morphology, and syntax, often complemented by phonetics, semantics, and pragmatics. There are currently two different approaches to the study of grammar, traditional grammar and theoretical grammar.