adjective (na)

Na-adjectives (なけいようし), also called adjectival nouns (けいようどうし), behave grammatically like nouns in many respects. In dictionary listings they appear without any ending (しずか, ゆうめい, しんせつ), but when directly modifying a noun they require the particle な: しずかなへや (a quiet room). As predicates, they connect to the sentence using だ (plain) or です (polite): このへやはしずかだ. Na-adjectives conjugate using the copula だ. Present negative: ～じゃない / ～ではない. Past affirmative: ～だった / ～でした. Past negative: ～じゃなかった. Te-form for listing: ～で (しずかでひろいへや — a quiet and spacious room). Adverbial form: ～に (しずかにはなす — speak quietly). Many na-adjectives are of Chinese origin (きれい, べんり, ふくざつ) and some are loanwords (ハンサム, カジュアル). A practical tip: if you can insert な between the word and a following noun naturally, it's a na-adjective. Watch out for words like きらい and きれい that end in い but are na-adjectives, not i-adjectives.