1A part-of-speech category in Japanese grammar for words like 「静かだ」 and 「元気だ」 that behave like nouns grammatically (taking だ/な/に) but express adjective-like meaning; commonly called "na-adjectives."
「きれいだ」「静かだ」は日本語文法で形容動詞と呼ばれる。
Words like 「きれいだ」 and 「静かだ」 are called na-adjectives (形容動詞) in Japanese grammar.
形容動詞は名詞を修飾するとき「な」の形になる（例：静かな夜）。
A na-adjective takes the form ending in "na" when modifying a noun (e.g., shizuka na yoru, "a quiet night").
日本語を教えるとき、形容詞と形容動詞の違いを説明するのは難しい。
When teaching Japanese, it's difficult to explain the difference between i-adjectives and na-adjectives (形容動詞).