substantive adjective
Linguistics term for an adjective that functions as a noun, often used in Japanese grammar to describe certain 形容動詞 or adjectival nouns.
Japanese 'shizuka' is given as an example of a substantive adjective.
形容動詞 (adjectival noun) is the more common term in Japanese school grammar for words like 静かだ; 名詞的形容詞 is a more technical linguistics term emphasizing noun-like behavior.
Compound of 名詞的 (substantive, noun-like) and 形容詞 (adjective), a calque from Western linguistics.