What is 形容動詞?
形容動詞 (けいようどうし) are a special class of words in Japanese that function like adjectives but are grammatically nouns. They are often called adjectival nouns or quasi-adjectives in English.
Usage and Grammar
Unlike true adjectives (形容詞), 形容動詞 require the copula "だ" or its polite form "です" to complete their predicate. For example, 静かだ (quiet) or 便利です (convenient). This is a key difference that learners should remember.
Common Collocations
- 形容動詞 + だ: Basic predicate form (e.g., 静かだ)
- 形容動詞 + ではない / じゃない: Negative form
- 形容動詞 + だった: Past tense
Register and Politeness
形容動詞 can be used in both casual and polite speech by changing the copula (だ / です). They are common in everyday conversation and writing.
Common Mistake
Learners sometimes forget to add "だ" after a 形容動詞 when making a statement, which sounds unnatural. Always remember that 形容動詞 need the copula unlike い-adjectives.