Japanese Grammar 14 – い-Adjectives · N5

📋 Formation Reference — い-Adjectives

How to conjugate い-adjectives in all forms. Press ▶ to hear examples.

CONJUGATION TABLE (おおきい = big)

Form	Rule	Example
Present ✓	[adj]い (です)	おおきい (です) ookii (desu)
Present ✗	[adj]くない (です)	おおきくない (です) ookikunai (desu)
Past ✓	[adj]かった (です)	おおきかった (です) ookikatta (desu)
Past ✗	[adj]くなかった (です)	おおきくなかった (です) ookikunakatta (desu)
Adverb	[adj]く	おおきくなる ookiku naru (become big)
Connecting	[adj]くて	おおきくてきれいな ookikute kireina (big and pretty)
+ Noun	[adj]い + noun	おおきいいえ ookii ie (big house)

EXCEPTION: いい (good)

Form	Correct	Wrong
Present ✓	いい / よい ii / yoi	—
Present ✗	よくない yokunai	✗ いくない
Past ✓	よかった yokatta	✗ いかった
Past ✗	よくなかった yokunakatta	✗ いくなかった

FORMULA — DROP い, ADD ENDING

[adj stem] ＋くない / かった / くなかった / くて

e.g. おおき- + kunai / katta / kunakatta / kute

→ Remove the final い, then attach the correct ending.

🗣 Example Sentences

See how い-adjectives work in context. Press ▶ to hear each sentence.

PRESENT FORMS

Example

このケーキはおいしいです。

Kono keeki wa oishii desu.

This cake is delicious.

このケーキはおいしいです

kono keeki wa oishii desu

→ "This cake is delicious." (い-adj + です)

Example

あたらしいくつがほしい。

Atarashii kutsu ga hoshii.

I want new shoes.

Example

このもんだいはむずかしくない。

Kono mondai wa muzukashikunai.

This problem is not difficult.

むずかし- ＋くない

muzukashi- + kunai

→ "is not difficult" (negative present)

PAST FORMS

Example

きのうはさむかったです。

Kinou wa samukatta desu.

It was cold yesterday.

さむ- ＋かった

samu- + katta

→ "was cold" (affirmative past)

Example

きょうはいそがしくなかったです。

Kyou wa isogashikunakatta desu.

I wasn't busy today.

Example

よかったですね！

Yokatta desu ne!

That's great! (Literally: That was good, wasn't it!)

CONNECTING & ADVERB FORMS

Example

やすくておいしいレストランをしっています。

Yasukute oishii resutoran wo shitte imasu.

I know a cheap and delicious restaurant.

やす- くておいしい

yasu- kute oishii

→ くて links two adjectives: "cheap and delicious"

Example

にほんごはおもしろくてたのしいです。

Nihongo wa omoshirokute tanoshii desu.

Japanese is interesting and fun.

📋 Quick-Reference Cheatsheet ▼

All conjugations: drop い, add the ending

✅ CORRECT

おおきくない

ookikunai

not big

Drop い from おおきい → おおき-, then add くない

❌ COMMON MISTAKE

おおきいくない

ookiikunai

intended: not big

Never keep い before adding the ending — always drop it first

いい is the ONLY exception — conjugates from よ-

✅ CORRECT

よかった / よくない

yokatta / yokunai

was good / not good

いい comes historically from よい — use よ- for all conjugated forms

❌ COMMON MISTAKE

いかった / いくない

ikatta / ikunai

intended: was good / not good

NEVER conjugate from い-. よかった and よくない are the only correct forms.

くて connects adjectives

✅ CORRECT

やすくておいしい

yasukute oishii

cheap and delicious

Use くて (not と or で) to chain い-adjectives

❌ COMMON MISTAKE

やすいとおいしい

yasui to oishii

intended: cheap and delicious

と connects nouns, not adjectives. Use くて to join い-adj descriptions.

い-adjective directly before a noun — no の or な needed

✅ CORRECT

おおきいいえ

ookii ie

big house

い-adjectives modify nouns directly — just place them before the noun

❌ COMMON MISTAKE

おおきないえ

ookina ie

intended: big house

おおきな exists but is a special form. Standard い-adj + noun = no な needed. Don't add の either.

A — Flashcards

Click a card to flip it. Use ▶ to hear the Japanese.

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B — Listen & Choose the Meaning

Press ▶ to hear each phrase, then choose the correct English meaning.

D — Listen & Write in Romaji

Press ▶ to hear each phrase, then type what you heard in romaji.

💡 Tip: Long vowels → double the vowel (おう = ou / oo). Double consonants → write them twice (きって = kitte).

📖 Grammar Deep Dive ▼

Why does いい become よ- when conjugated?

いい is the modern spoken form of the classical adjective よい (yoi). In everyday speech, the present plain form いい is standard, but ALL conjugated forms still come from よ-. This is a historical survival — the stem never changed under the surface.

  • いい → よくない (not good)
  • いい → よかった (was good)
  • いい → よくなかった (was not good)
  • いい → よくて (good and…)

Think of it as: the word "shows its face" as いい but "works" as よ-.

てんきがよかったですね。

Tenki ga yokatta desu ne.

The weather was nice, wasn't it.

い-adj vs な-adj — and tricky exceptions

A common trap: words ending in い are NOT always い-adjectives. Three important な-adjectives look like い-adjectives but are NOT:

  • きれい (pretty) → きれいなひと ✅ / きれいくない ✗
  • ゆうめい (famous) → ゆうめいなみせ ✅
  • きらい (dislike) → きらいなたべもの ✅

Test: if a word uses な before a noun and ではない/じゃない in the negative, it is a な-adjective regardless of its ending.

きれいなはながあります。

Kireina hana ga arimasu.

There are pretty flowers.

The adverb form — [adj]く

Drop い and add く to turn an い-adjective into an adverb. This く-form modifies verbs, not nouns.

  • はやい (fast) → はやくはしる (run fast)
  • おおきい (big) → おおきくなる (become big)
  • やさしい (kind) → やさしくおしえる (teach kindly)

The く-form is also the base for なる (become) constructions: あたらしくなる = become new.

[adj stem] く verb

[stem] ku verb

→ adverb + verb phrase

はやくおきてください。

Hayaku okite kudasai.

Please wake up early (quickly).

Degree words with い-adjectives

Intensifiers and softeners go directly before the adjective:

  • すごく / とても + adj = very [adj] (strong intensity)
  • ちょっと + adj = a little [adj]
  • あまり + negative = not very [adj]

Note: あまり must pair with a negative form — never with a positive.

このほんはあまりおもしろくない。

Kono hon wa amari omoshirokunai.

This book is not very interesting.

すぎる — expressing excess

Attach すぎる to the く-stem (the adverb form) to mean "too [adj]":

  • たかい → たかすぎる (too expensive)
  • おおきい → おおきすぎる (too big)
  • さむい → さむすぎる (too cold)

Because すぎる is itself a verb (to exceed), the full phrase conjugates like a verb, not an adjective.

[adj stem] すぎる

[stem] sugiru

→ "too [adjective]"

このかばんはたかすぎます。

Kono kaban wa takasugimasu.

This bag is too expensive.

📝 Key Vocabulary ▼

Japanese	Romaji	English
おおきい	ookii	big, large
ちいさい	chiisai	small, little
たかい	takai	expensive; tall; high
やすい	yasui	cheap, inexpensive
あたらしい	atarashii	new
ふるい	furui	old (things, not people)
おいしい	oishii	delicious, tasty
さむい	samui	cold (weather/air)
あつい	atsui	hot
むずかしい	muzukashii	difficult
おもしろい	omoshiroi	interesting, funny
たのしい	tanoshii	fun, enjoyable