 Adjective

An adjective is a part of speech characteristically used to express properties and modify nouns. It can also occur in predicative constructions, as in The cube is red. Its classification depends on its grammatical behavior, beyond whether its meaning sounds descriptive.^[ref]

In an original simple formal semantics, let red objects form $R=\{1,2\}$ and cubes form $C=\{2,3\}$. The expression red cube can denote the intersection $R\cap C=\{2\}$. This illustrates how an adjective can contribute a property to a noun phrase, while leaving the grammatical classification distinct from that particular semantic rule.

Modification alone is insufficient evidence for adjective status. In the Universal Dependencies scheme, a noun used to modify another noun in a compound remains tagged as a noun. Clear category criteria make linguistic annotation reproducible instead of treating every modifier as the same class.