JLPT N5 Grammar: i‑adjectives
Complete conjugation — present, negative, past, and past negative
JLPT N5 文法 い形容詞 活用 (い・くない・かった・くなかった)
⏱️ Study time: 7–10 minutes
i‑adjectives are words that end in い and describe nouns directly. They have their own conjugation system — you don't use です to make them negative or past. Instead, the い changes to く (negative) or かった (past). This lesson covers all four core forms in polite Japanese.
⚡ Four Forms of i‑adjectives at a Glance
Present Affirmative — 〜いです
The simplest form. Take the i‑adjective as it is and add です for politeness. This describes something in the present or future.
おいしいです
It is delicious.
たのしいです
It is fun.
おおきいです
It is big.
ちいさいです
It is small.
Negative — 〜くないです
Drop the final い and add くないです. This is the standard polite negative for all i‑adjectives.
→ おいしくないです
It is not delicious.
→ たのしくないです
It is not fun.
→ あつくないです
It is not hot.
→ さむくないです
It is not cold.
Past — 〜かったです
Drop the final い and add かったです. This describes something that was a certain way in the past.
→ おいしかったです
It was delicious.
→ たのしかったです
It was fun.
→ あつかったです
It was hot.
→ さむかったです
It was cold.
Past Negative — 〜くなかったです
Drop the final い and add くなかったです. This describes something that was not a certain way in the past.
→ おいしくなかったです
It was not delicious.
→ たのしくなかったです
It was not fun.
→ あつくなかったです
It was not hot.
→ さむくなかったです
It was not cold.
📊 Complete Conjugation Table
Examples & Mini Dialogue
昨日は暑かったです。きのうはあつかったです。Kinō wa atsukatta desu.
Yesterday was hot.
✅ Past form of あつい.
この本はおもしろくなかったです。このほんはおもしろくなかったです。Kono hon wa omoshirokunakatta desu.
This book was not interesting.
A: 日本語の勉強はどうですか。にほんごのべんきょうはどうですか。Nihongo no benkyō wa dō desu ka.
B: 難しいですが、楽しいです。むずかしいですが、たのしいです。Muzukashii desu ga, tanoshii desu.
Common Mistakes (and Fixes)
JLPT N5 Practice Questions
1. What is the negative of たかい (expensive)?
2. What is the past form of さむい (cold)?
3. What is the past negative of おいしい (delicious)?
4. i‑adjectives __________ use ではありません for the negative.
Test yourself with a free mock exam →
About the Instructor
Taught by Anup Sensei at Gogaku Language & Training Center in Pokhara. With real Japan experience and a focus on exam essentials, he helps students pass the JLPT with confidence.
⚡ Vocabulary Used in This Lesson
Related Grammar
Frequently Asked Questions
Why can't I use じゃない with i‑adjectives?
じゃない and ではありません are the negative forms of the copula です, used for nouns and na‑adjectives. i‑adjectives contain their own built‑in copula (the い), so they have their own negative form: くない.
What about the casual forms?
In casual speech, you drop です: おいしい, おいしくない, おいしかった, おいしくなかった. The conjugation of the adjective itself is identical.
Is いい (good) an i‑adjective?
Yes, but it is irregular. Its negative is よくない, past is よかった, past negative is よくなかった. The root changes from い to よ.
Continue Learning
Next: な‑adjectives — the other adjective group.
Learn な‑adjectives →→ Explore the JLPT N5 Grammar Hub
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