い-Adjective Conjugation Core
い-adjectives carry their own tense and negation (like verbs). You conjugate by dropping the final い and adding the ending — no だ/です needed to be grammatical.
Structure
Stem (drop い) + い (present) / くない (negative) / かった (past) / くなかった (past negative)
Examples
暑い → 暑くない / 暑かった / 暑くなかった
atsui → atsukunai / atsukatta / atsukunakatta
hot → not hot / was hot / was not hot
Each form drops the final い and adds the ending (くない / かった / くなかった)
いい → よくない / よかった / よくなかった
ii → yokunai / yokatta / yokunakatta
good → not good / was good / was not good
Irregular: いい comes from よい, so every conjugated form uses the よ- stem
寒い → 寒くない / 寒かった / 寒くなかった
samui → samukunai / samukatta / samukunakatta
cold → not cold / was cold / was not cold
Regular pattern: drop the final い and add くない / かった / くなかった
• い-adjectives don't need だ/です to be grammatical: 寒い。('It's cold.') is a complete sentence. Adding です (寒いです) just makes it polite — you never say 寒いだ. • Irregular いい/よい is the one to memorise.
Commonly confused with
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones い-Adjective is tested against.
vs な-adjectives
い-adjectives conjugate themselves (暑かった); な-adjectives don't — they rely entirely on the copula (静かだった) and need な before a noun.
More adjectives
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