What are I-adjectives?
I-adjectives (い形容詞) are adjectives that end in い in their dictionary form. They conjugate like verbs and can stand alone as predicates.
高い (takai) - expensive, tall, high
大きい (ookii) - big
美味しい (oishii) - delicious
楽しい (tanoshii) - fun, enjoyable
Characteristics
1. Always End in い
高い - expensive
安い - cheap
新しい - new
古い - old
2. Conjugate Independently
Unlike na-adjectives, they don't need です:
高い ✓ "It's expensive"
高いです ✓ "It's expensive" (polite)
3. Modify Nouns Directly
高い車 - expensive car
大きい家 - big house
美味しい料理 - delicious food
Common I-adjectives
Size
大きい (ookii) - big
小さい (chiisai) - small
長い (nagai) - long
短い (mijikai) - short
広い (hiroi) - wide, spacious
狭い (semai) - narrow, cramped
高い (takai) - tall, high
低い (hikui) - low, short (height)
Quality
良い (yoi/ii) - good
悪い (warui) - bad
新しい (atarashii) - new
古い (furui) - old
正しい (tadashii) - correct
間違い (machigai) - wrong (noun, not adjective)
Price/Value
高い (takai) - expensive
安い (yasui) - cheap
Taste
美味しい (oishii) - delicious
不味い (mazui) - bad-tasting
甘い (amai) - sweet
辛い (karai) - spicy, salty
苦い (nigai) - bitter
酸っぱい (suppai) - sour
Temperature
暑い (atsui) - hot (weather)
寒い (samui) - cold (weather)
熱い (atsui) - hot (objects)
冷たい (tsumetai) - cold (objects)
温かい (atatakai) - warm
涼しい (suzushii) - cool
Feelings
嬉しい (ureshii) - happy, glad
楽しい (tanoshii) - fun, enjoyable
悲しい (kanashii) - sad
恐ろしい (osoroshii) - frightening
恥ずかしい (hazukashii) - embarrassing
Difficulty
難しい (muzukashii) - difficult
易しい (yasashii) - easy
忙しい (isogashii) - busy
Physical State
痛い (itai) - painful
眠い (nemui) - sleepy
重い (omoi) - heavy
軽い (karui) - light (weight)
Colors (Some)
赤い (akai) - red
青い (aoi) - blue
白い (shiroi) - white
黒い (kuroi) - black
黄色い (kiiroi) - yellow
茶色い (chairoi) - brown
How to Use I-adjectives
1. Modifying Nouns
Place before the noun:
高い車
"expensive car"
美味しい食べ物
"delicious food"
大きい犬
"big dog"
新しい本
"new book"
2. As Predicate (です Optional)
この車は高い
"This car is expensive"
この車は高いです
"This car is expensive" (polite)
3. Multiple Adjectives
大きくて白い犬
"a big, white dog"
安くて美味しいレストラン
"a cheap and delicious restaurant"
Special I-adjective: いい/よい
Good has two forms:
いい (ii) - casual, more common
よい (yoi) - formal, traditional
Both mean "good" but conjugate from よい:
Present: いい / よい
Negative: よくない (NOT いくない)
Past: よかった
Identifying I-adjectives
True I-adjectives
Must end in い preceded by:
- あ, い, う, え, or お sound
高い (taka-i) ✓
大きい (ooki-i) ✓
美味しい (oishi-i) ✓
Not I-adjectives
Some words end in い but aren't adjectives:
嫌い (kirai) - dislike (na-adjective!)
きれい (kirei) - pretty (na-adjective!)
有名 (yuumei) - famous (na-adjective!)
Rule: If it looks foreign or can't conjugate as い-adjective, it's probably な-adjective!
Sentence Patterns
Basic Statement
この本は面白い
"This book is interesting"
東京は大きい
"Tokyo is big"
With です (Polite)
この本は面白いです
"This book is interesting"
東京は大きいです
"Tokyo is big"
Question Form
この本は面白いですか？
"Is this book interesting?"
日本語は難しいですか？
"Is Japanese difficult?"
Common Mistakes
Mistake 1: Adding な to I-adjectives
Wrong: 高いな車 ❌
Right: 高い車 ✓
"expensive car"
い-adjectives modify directly!
Mistake 2: Thinking All い Words are I-adjectives
Wrong: きれい is i-adjective ❌
Right: きれい is na-adjective ✓
きれいな花 ✓ "beautiful flower"
Mistake 3: Wrong Conjugation of いい
Wrong: いくない ❌
Right: よくない ✓
"not good"
Wrong: いかった ❌
Right: よかった ✓
"was good"
Mistake 4: Using です Before Noun
Wrong: 高いです車 ❌
Right: 高い車 ✓
Right: 車は高いです ✓
I-adjectives vs Na-adjectives
| I-adjectives | Na-adjectives |
|---|---|
| End in い | Various endings |
| 高い車 | 静かな車 |
| Conjugate like verbs | Need な/だ |
| Native Japanese | Often foreign origin |
Examples
I-adjective:
高い車 "expensive car"
車は高い "the car is expensive"
Na-adjective:
静かな車 "quiet car"
車は静かだ "the car is quiet"
Describing Things
Objects
大きい箱
"big box"
重い荷物
"heavy luggage"
新しいパソコン
"new computer"
Places
広い部屋
"spacious room"
高い山
"tall mountain"
古い町
"old town"
Food
美味しい料理
"delicious dish"
辛い食べ物
"spicy food"
甘いケーキ
"sweet cake"
People (Appearance/State)
若い人
"young person"
忙しい学生
"busy student"
眠い子供
"sleepy child"
Conversation Examples
Example 1: Shopping
A: この服はどうですか？
"How is this clothing?"
B: 高いですね
"It's expensive"
A: じゃあ、こっちは？
"Then, how about this one?"
B: 安くていいですね
"It's cheap and good"
Example 2: Food
A: このレストランはどう？
"How's this restaurant?"
B: 美味しいよ
"It's delicious"
A: 高い？
"Is it expensive?"
B: いいえ、安いよ
"No, it's cheap"
Example 3: Weather
A: 今日は暑いね
"It's hot today"
B: 本当に。昨日は涼しかったのに
"Really. Yesterday was cool though"
Key Patterns
Asking Opinions
どうですか？
"How is it?"
美味しいですか？
"Is it delicious?"
難しいですか？
"Is it difficult?"
Describing
とても大きい
"very big"
ちょっと高い
"a little expensive"
あまり面白くない
"not very interesting"
Key Takeaways
✓ I-adjectives end in い
✓ Modify nouns directly (no な)
✓ Conjugate independently
✓ Can be predicate without です
✓ いい conjugates from よい
✓ Not all い words are i-adjectives
✓ Native Japanese words
✓ Essential for descriptions
Master i-adjectives - they're everywhere in Japanese!
Next: Na-adjectives (な形容詞)
Related: