い-adjectivesi-adjectives“Japanese i-adjectives explained”

い-adjectives are describing words that end in い: 高い (expensive), 寒い (cold), おもしろい (interesting), 新しい (new). What makes them special is that they conjugate on their own. The adjective itself changes to show past tense and negation, the same way a verb does. That is the main thing to learn at JLPT N5.

English says "was cold". Japanese says 寒かった. The past tense lives inside the い-adjective, not in a helper word.

What does い-adjectives mean?

“い-adjective” is the name of a word class, not one piece of grammar. It covers every adjective whose dictionary form ends in い and conjugates by changing that final い. Some very common ones:

• 大きい (big), 小さい (small)
• 高い (expensive, tall), 安い (cheap)
• 暑い (hot, for weather), 寒い (cold)
• おいしい (tasty), 楽しい (fun), 難しい (difficult)
• いい (good), 悪い (bad)

You use them in two positions. Before a noun, they describe it: 高い店 (an expensive shop). At the end of a sentence, they say something about the topic: 店は高いです (the shop is expensive).

How to form い-adjectives

Before a noun, the adjective goes straight in front with nothing between:

To conjugate, drop the final い and add an ending:

Two more forms you will see at N5:

• て-form for joining adjectives: 高い → 高くて. この部屋は広くて明るいです (This room is big and bright).
• く-form as an adverb: 早い → 早く. 早く起きます (I get up early).

⚠️ The one irregular: いい (good) conjugates from its old form よい. So it is よくない, よかった, よくなかった, よくて. Never いくない or いかった. The same applies to words that end in いい, like かっこいい → かっこよくない.

In polite speech, です after an い-adjective only adds politeness. It never carries tense. That is why the past is 高かったです, with the past already inside the adjective.

When is い-adjectives used?

You use い-adjectives any time you describe how something is: weather, food, prices, size, feelings about an experience. They are neutral in register. Add です for polite speech, and leave it off with friends:

• Friend: このラーメン、おいしい！
• Waiter: このラーメンはおいしいです。

In casual speech, a bare い-adjective is a complete sentence. You do not need だ after it, and 高いだ is wrong. This is one of the clearest differences from nouns and な-adjectives, which take だ in plain speech.

い-adjectives example sentences

In the fifth sentence, notice あまり + negative (“not very”). That pairing shows up constantly with い-adjectives: あまり高くない, あまりおいしくなかった.

Nuance of い-adjectives

Watch out for words that only look like い-adjectives. きれい (pretty, clean), きらい (dislike), ゆうめい (famous) and しつれい (rude) all end in い, but they are な-adjectives. The い is part of the stem, so it does not drop: きれいじゃない, not きれくない. You just have to memorise these few.

大きい and 小さい have a second form. Before nouns, you will also see 大きな and 小さな: 大きな木 (a big tree). This is a fixed set phrase, not a sign that 大きい is a な-adjective. At N5, 大きい木 and 大きな木 are both fine.

暑い vs 熱い vs 寒い vs 冷たい. English “hot” and “cold” split in Japanese. 暑い and 寒い describe the air or weather. 熱い and 冷たい describe things you touch: 熱いお茶 (hot tea), 冷たい水 (cold water). Test questions like to check this.

Feelings about yourself. Adjectives like 痛い (painful) and 寂しい (lonely) describe your own feelings directly: 頭が痛い (my head hurts). You do not say them this way about another person’s feelings. Other people’s feelings need extra grammar you will meet at N4.

い-adjectives vs な-adjectives

The two adjective types mean the same kind of thing, but they attach and conjugate differently.

A quick test: if you can drop the い and add かった to get a real word, it is an い-adjective. For the full な-adjective patterns, see な-adjectives.

Common mistakes with い-adjectives

Is い-adjectives on the JLPT?

A common grammar item gives you 「きのうは　さむ（　）です。」 and asks you to pick かった over かったでした or いでした. Listening questions often hinge on hearing くない versus い, so practise saying the negative forms out loud.

Practice questions for い-adjectives

Learning path for い-adjectives

Related grammar to review next

• な-adjectives — the other adjective type, which conjugates with だ instead of changing its ending
• なる — uses the く-form of い-adjectives to say something changes: 高くなる
• すぎる — attaches to the stem after dropping い: おいしすぎる, 高すぎる
• とても — the most common intensifier in front of い-adjectives
• は〜より・・・です — the comparison frame that almost always ends in an adjective

Learn い-adjectives with Hane

Hane has you conjugate real い-adjectives, including いい and the tricky look-alikes like きれい, until the forms come out automatically. Practice with Hane.