From The Art and Popular Culture Encyclopedia
"That poetry is like the arts of painting, cooking, and cosmetics in its ability to express every sensation of sweetness or bitterness, of beatitude or horror, by coupling a certain noun with a certain adjective, in analogy or contrast" --unpublished preface to The Flowers of Evil, tr. Marthiel and Jackson Mathews [...]
"If one looks at the normal practice of music criticism (or, which is often the same thing, of conversations “on” music), it can readily be seen that a work (or its performance) is only ever translated into the poorest of linguistic categories: the adjective. Music, by natural bent, is that which at once receives an adjective."--"The Grain of the Voice" (1982) by Roland Barthes
In grammar, an adjective is a word whose role is to modify a noun or pronoun (called the adjective's subject, giving more information about what the noun or pronoun refers to. Collectively, adjectives form one of the traditional eight parts of speech, though linguists today distinguish adjectives from words such as determiners that used to be considered adjectives but that are now recognized to be different.
Not all languages have adjectives, but most, including English, do. (English adjectives include big, old, and tired, among many others.) Those that don't 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 a 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, where English has "to be hungry" (hungry being an adjective), French has "avoir faim" (literally "to have hunger"), and where Hebrew has the adjective "צריך" (roughly "in need of"), English uses the verb "to need".
Classes of adjectives
There are 6 classes of adjectives in the English language:
Numeric: six, three hundred
Quantitative: more, all, some, half, more than enough
Qualitative: Relates to colour, size, smell etc.
Possessive: my, his, their, your
Interrogative: which, whose, what
Demonstrative: this, that, those, these