How to Conjugate Japanese Adjectives: i & na with Examples

Adjectives in Japanese are sneaky. At first glance, they look like English adjectives—simple describing words. But the moment you try to say things like "it was delicious" or "it isn't quiet," you quickly realize Japanese is doing something completely different.

There isn't just one adjective system. There are two, and they don't follow the same rules. One behaves like a verb. The other behaves like a noun wearing an adjective costume. And if you treat them the same, your sentences start sounding like scrambled eggs.

The good news? Once you learn how to tell them apart—and how each one transforms—Japanese suddenly becomes predictable, even logical. Let's decode the system so adjectives work for you, not against you.

Table of Contents

• What Makes Japanese Adjectives Different?
• The Two Types: i-Adjectives vs na-Adjectives
• How to Identify Each Type
• i-Adjective Conjugation (Step by Step)
• The Special Case: いい (good)
• na-Adjective Conjugation (Step by Step)
• Complete Conjugation Tables
• Using Adjectives to Modify Nouns
• Te-form for Both Types
• Advanced Forms and Patterns
• Common Mistakes to Avoid
• Real Conversation Examples

What Makes Japanese Adjectives Different?

In English, adjectives are simple: "big," "beautiful," "expensive." They don't change regardless of tense or context.

Japanese adjectives are more dynamic. They conjugate to show:

• Tense (present vs. past)
• Polarity (positive vs. negative)
• Formality (casual vs. polite)
• Connection (linking multiple descriptions)

Quick comparison:

See how the adjective itself changes? That's conjugation in action.

The Two Types: i-Adjectives vs na-Adjectives

Japanese has two distinct adjective categories, each conjugating differently.

i-Adjectives (形けい容よう詞し)

Key characteristic: Always end in い (i) that conjugates

These are "true" adjectives that conjugate similarly to verbs. The い ending is part of the adjective itself and changes during conjugation.

Common examples:

• 大おおきい (ookii) - big
• 小ちいさい (chiisai) - small
• おいしい (oishii) - delicious
• 高たかい (takai) - expensive/tall
• 新あたらしい (atarashii) - new

na-Adjectives (形けい容よう動どう詞し)

Key characteristic: Need な (na) before nouns

These are actually "adjectival nouns" that behave more like nouns. They conjugate using だ/です.

Common examples:

• 静しずか (shizuka) - quiet
• 便べん利り (benri) - convenient
• 有ゆう名めい (yuumei) - famous
• きれい (kirei) - beautiful/clean
• 好すき (suki) - liked

How to Identify Each Type

For i-adjectives:

1. Always ends in い
2. The い is part of the base adjective
3. Conjugates by changing the い ending
4. Does NOT need な before nouns

Test: Try removing the い. If what's left isn't a word on its own, it's an i-adjective.

• 大おおきい → おおき (not a word) ✓ i-adjective

For na-adjectives:

1. Doesn't end in い, OR ends in い but the い isn't part of conjugation
2. Uses な when modifying nouns directly
3. Conjugates like nouns (using だ/です)

Notable na-adjectives that end in い:

• きれい (kirei) - beautiful
• 嫌きらい (kirai) - disliked
• 幸さいわい (saiwai) - fortunate

i-Adjective Conjugation (Step by Step)

i-adjectives conjugate by changing the い ending. Think of い as having different "forms" just like verb endings.

Important note: The negative ending ない is itself an i-adjective, which is why negative forms can conjugate further (なかった, なくて).

Present Tense (Polite)

Rule: Keep the adjective as-is + です

高たかいです
Takai desu
"It's expensive"

おいしいです
Oishii desu
"It's delicious"

Present Tense (Casual)

Rule: Just use the adjective as-is

高たかい
Takai
"It's expensive"

おいしい
Oishii
"It's delicious"

Negative Form

Rule: Change い → く + ない (+ です for polite)

Translation: "not expensive," "not delicious," "not cold"

Past Tense

Rule: Change い → かった (+ です for polite)

Translation: "was expensive," "was delicious," "was fun"

Past Negative

Rule: Change い → く + なかった (+ です for polite)

Translation: "wasn't expensive," "wasn't delicious"

Te-form (Connecting)

Rule: Change い → くて

Used to connect multiple adjectives or lead into other grammar patterns.

安やすくて、おいしいです
Yasukute, oishii desu
"It's cheap and delicious"

大おおきくて重おもいです
Ookikute omoi desu
"It's big and heavy"

Adverbial Form

Rule: Change い → く

Turns the adjective into an adverb (describes how an action is done).

速はやく走はしる
Hayaku hashiru
"Run quickly"

早はやく起おきる
Hayaku okiru
"Wake up early"

The Special Case: いい (good)

The adjective いい (good) is irregular. Its stem is actually よ in all conjugations except the present tense.

na-Adjective Conjugation (Step by Step)

na-adjectives conjugate exactly like nouns using だ/です. Much simpler!

Present Tense

Polite: [adjective] + です
Casual: [adjective] + だ

静しずかです / 静しずかだ
Shizuka desu / Shizuka da
"It's quiet"

便べん利りです / 便べん利りだ
Benri desu / Benri da
"It's convenient"

Negative Form

Polite: [adjective] + ではありません / じゃありません
Casual: [adjective] + ではない / じゃない

静しずかではありません
Shizuka dewa arimasen
"It's not quiet" (formal)

静しずかじゃないです
Shizuka janai desu
"It's not quiet" (conversational)

静しずかじゃない
Shizuka janai
"It's not quiet" (casual)

Formality levels:

• じゃない(です) = conversational
• ではありません = formal/written

Past Tense

Polite: [adjective] + でした
Casual: [adjective] + だった

静しずかでした / 静しずかだった
Shizuka deshita / Shizuka datta
"It was quiet"

Past Negative

Polite: [adjective] + ではありませんでした / じゃありませんでした
Casual: [adjective] + ではなかった / じゃなかった

静しずかではありませんでした
Shizuka dewa arimasen deshita
"It wasn't quiet" (formal)

静しずかじゃなかったです
Shizuka janakatta desu
"It wasn't quiet" (conversational)

静しずかじゃなかった
Shizuka janakatta
"It wasn't quiet" (casual)

Te-form (Connecting)

Rule: [adjective] + で

静しずかできれいです
Shizuka de kirei desu
"It's quiet and beautiful"

Complete Conjugation Tables

i-Adjective Full Table

Example: 大おおきい (ookii - big)

na-Adjective Full Table

Example: 静しずか (shizuka - quiet)

Using Adjectives to Modify Nouns

This is where the names "i-adjective" and "na-adjective" really make sense.

i-Adjectives Before Nouns

Rule: Just place the adjective directly before the noun (no particle needed)

大おおきい家いえ
Ookii ie
"A big house"

おいしい料りょう理り
Oishii ryouri
"Delicious food"

新あたらしい車くるま
Atarashii kuruma
"A new car"

na-Adjectives Before Nouns

Rule: Add な between the adjective and noun

静しずかな場ば所しょ
Shizuka na basho
"A quiet place"

便べん利りな道どう具ぐ
Benri na dougu
"A convenient tool"

きれいな花はな
Kirei na hana
"A beautiful flower"

Te-form for Both Types

The te-form connects multiple descriptions in one sentence.

Connecting Same Type Adjectives

i-adjectives:

この部へ屋やは広ひろくて、明あかるいです。
Kono heya wa hirokute, akarui desu.
"This room is spacious and bright."

na-adjectives:

彼かれは親しん切せつで優やさしいです。
Kare wa shinsetsu de yasashii desu.
"He is kind and gentle."

Connecting Mixed Types

You can mix i- and na-adjectives in the same sentence:

この町まちは静しずかで美うつくしいです。
Kono machi wa shizuka de utsukushii desu.
"This town is quiet and beautiful."

(静か is na-adjective first, 美しい is i-adjective)

Pattern note: When connecting na-adjective → i-adjective, the na-adjective uses で, and the i-adjective stays in its base form.

Learn more about te-form patterns in our complete te-form lesson

Advanced Forms and Patterns

Conditional Forms (If...)

i-adjectives: Change い → ければ

安やすければ買かいます。
Yasukereba kaimasu.
"If it's cheap, I'll buy it."

i-adjectives (colloquial/spoken): Use past tense + ら

高たかかったら、買かいません。
Takakattara, kaimasen.
"If it's expensive, I won't buy it."

na-adjectives (formal): Add なら

便べん利りなら使つかいます。
Benri nara tsukaimasu.
"If it's convenient, I'll use it."

na-adjectives (colloquial): Use だったら

便べん利りだったら使つかいます。
Benri dattara tsukaimasu.
"If it's convenient, I'll use it."

Adverbial Forms (Turning into Adverbs)

i-adjectives: Change い → く

速はやく走はしる
Hayaku hashiru
"Run quickly"

早はやく起おきる
Hayaku okiru
"Wake up early"

na-adjectives: Add に

静しずかに歩あるく
Shizuka ni aruku
"Walk quietly"

きれいに書かく
Kirei ni kaku
"Write neatly"

Comparison:

• i-adj → く: 速く走る (run quickly)
• na-adj → に: 静かに話す (speak quietly)

Noun Form ("ness")

i-adjectives: Change い → さ

大おおきさ - size (bigness)
高たかさ - height (tallness)
美うつくしさ - beauty (beautifulness)

This ～さ pattern is highly productive and works with most i-adjectives.

Degree Modifiers

Common words that intensify or modify adjectives:

とても (totemo) - very
とてもおいしい "Very delicious"

すごく (sugoku) - extremely (casual)
すごく大おおきい "Extremely big"

かなり (kanari) - fairly/quite
かなり高たかい "Fairly expensive"

けっこう (kekkou) - quite/rather
けっこうおいしい "Quite delicious" (often pleasantly surprising)

ちょっと (chotto) - a little/somewhat
ちょっと高たかい "A little expensive"

あまり + negative - not very
あまりおいしくない "Not very delicious"

Common Mistakes to Avoid

Using です with i-adjective Past Tense Incorrectly

Why: The adjective itself conjugates to past tense (かった), then you add です.

Forgetting な with na-Adjectives

Treating きれい as an i-Adjective

Remember: きれい is a na-adjective despite ending in い!

Double Conjugation with na-Adjectives

Why: Don't add both だ and じゃない. The negative replaces だ entirely.

Forgetting いい is Irregular

Why: いい uses the stem よ for all conjugations except present tense.

Real Conversation Examples

At a Restaurant

Waiter: お料りょう理りはどうでしたか？
O-ryouri wa dou deshita ka?
"How was the food?"

You: とてもおいしかったです！
Totemo oishikatta desu!
"It was very delicious!"

You: でも、ちょっと高たかかったです。
Demo, chotto takakatta desu.
"But it was a little expensive."

Shopping for Apartments

Agent: こちらの部へ屋やは広ひろくて明あかるいです。
Kochira no heya wa hirokute akarui desu.
"This room is spacious and bright."

You: 静しずかですか？
Shizuka desu ka?
"Is it quiet?"

Agent: はい、とても静しずかで便べん利りな場ば所しょです。
Hai, totemo shizuka de benri na basho desu.
"Yes, it's a very quiet and convenient location."

Describing Your Day

今日きょうは忙いそがしかったです。
Kyou wa isogashikatta desu.
"Today was busy."

朝あさは寒さむかったですが、午ご後ごは暖あたたかくなりました。
Asa wa samukatta desu ga, gogo wa atatakaku narimashita.
"The morning was cold, but the afternoon became warm."

Comparing Things

A: この車くるまと車くるま、どっちがいいですか？
Kono kuruma to kuruma, dotchi ga ii desu ka?
"Between these two cars, which is better?"

B: 赤あかい車くるまのほうが新あたらしくて速はやいです。
Akai kuruma no hou ga atarashikute hayai desu.
"The red car is newer and faster."

Practice Exercises

Try conjugating these adjectives (answers at the end):

Exercise 1: i-Adjectives

Convert 寒さむい (cold) to:

1. Past tense (polite)
2. Negative (polite)
3. Past negative (casual)
4. Te-form

Exercise 2: na-Adjectives

Convert 便べん利り (convenient) to:

1. Past tense (polite)
2. Negative (casual)
3. Before a noun (+ 店みせ)
4. Te-form

Exercise 3: Mixed Practice

Translate to Japanese:

1. "This restaurant is cheap and delicious."
2. "The room was quiet but not very clean."
3. "If it's expensive, I won't buy it."

Exercise 4: いい (irregular)

Conjugate いい:

1. Negative (casual)
2. Past (polite)
3. Adverb form

The Bottom Line

Japanese adjective conjugation might seem complicated at first, but it follows clear, consistent patterns. Here's what to remember:

i-Adjectives:

• End in い that conjugates: い → かった / くない / くて
• Conjugate like their own little verb system
• Don't need な before nouns
• Exception: いい uses よ stem in all forms except present

na-Adjectives:

• Conjugate exactly like nouns (use だ/です)
• Need な when modifying nouns directly
• Some end in い but don't conjugate that ending (like きれい!)

Key Success Tips:

1. Learn the type first - Is it i- or na-? This determines everything
2. Master いい early - It's irregular and extremely common
3. Practice both types equally - Don't neglect na-adjectives
4. Use real sentences - Tables help, but sentences stick
5. Watch for exceptions - きれい, きらい, ゆうめい are all na-adjectives

Once these patterns become automatic, you'll find yourself naturally conjugating adjectives without thinking. The beauty of the system is its consistency—once you know the rules, you can handle thousands of adjectives with confidence.

Ready to practice? Explore our complete adjectives database where every adjective includes full conjugation tables, audio pronunciation, and real example sentences. Or dive deeper with our interactive adjectives lesson

頑がん張ばって！(Keep practicing!)