Japanese i-Adjectives: Rules, Conjugation, Examples and Exceptions

Japanese i-adjectives, or keiyoushi [形容詞], are one of the foundations of beginner grammar. They describe qualities such as size, color, emotion, weather, and taste, and they can appear both before a noun and at the end of a sentence.

This guide explains what makes an adjective an i-adjective, how the main conjugations work, which words often confuse learners, and a practical list of common adjectives that you will see often in everyday Japanese.

If you want to expand this topic later, our guide to the -sa, -sou and -me adjective forms is a natural next step after the basics below.

Contents 11

What makes an adjective an i-adjective?

A true i-adjective ends in the hiragana い and can conjugate by changing that final sound. Common examples include takai [高い, expensive or tall], atsui [暑い, hot], and omoshiroi [面白い, interesting].

The important detail is that not every word that sounds like it ends in i is an i-adjective. Some very common words, especially kirei [きれい, pretty or clean] and kirai [きらい, disliked], are actually na-adjectives.

Type	Example	Meaning	Before a noun
i-adjective	高い	expensive, tall	高い店
na-adjective	きれい	pretty, clean	きれいな部屋

That difference matters because i-adjectives do not need na before a noun, while na-adjectives do.

How i-adjectives work in a sentence

You can use an i-adjective directly before a noun:

• 高い店 [takai mise] = an expensive shop
• 新しい本 [atarashii hon] = a new book
• 忙しい人 [isogashii hito] = a busy person

You can also place it at the end of a sentence. In polite speech, desu is often added after the adjective:

• この店は高いです。 [Kono mise wa takai desu.] = This shop is expensive.
• 今日は寒いです。 [Kyou wa samui desu.] = It is cold today.

Once you understand this pattern, the next step is learning how the final i changes in common conjugations.

Basic conjugation of Japanese i-adjectives

For most i-adjectives, the rule is simple: remove the final i and add a new ending. Beginners should focus first on the four forms used all the time: present, negative, past, and past negative.

Function	Pattern	Example with 高い	Meaning
Present	base form	高い	expensive, tall
Negative	-くない	高くない	not expensive, not tall
Past	-かった	高かった	was expensive, was tall
Past negative	-くなかった	高くなかった	was not expensive, was not tall
Te form	-くて	高くて	and, because it is expensive
Adverbial	-く	早く	quickly
Conditional	-ければ	高ければ	if it is expensive, if it is tall
Too much	-すぎる	高すぎる	too expensive, too tall
Looks like	-そう	高そう	looks expensive

The te form is especially useful when you want to connect ideas. For a broader explanation of how this linking pattern works in grammar, see our article about the Japanese te form.

Negative form with -kunai

To make most i-adjectives negative, change the final i to kunai:

• 暑い → 暑くない [atsui → atsukunai] = not hot
• 面白い → 面白くない [omoshiroi → omoshirokunai] = not interesting

In polite speech, learners often say 暑くないです. That pattern is common and natural in everyday conversation.

Past form with -katta

To talk about the past, replace the final i with katta:

• 寒い → 寒かった [samui → samukatta] = it was cold
• 楽しい → 楽しかった [tanoshii → tanoshikatta] = it was fun

The past negative follows the same logic:

• 寒くなかった [samukunakatta] = it was not cold
• 楽しくなかった [tanoshikunakatta] = it was not fun

Te form, adverbial form, and naru

The ku stem appears in several useful structures. With te, it links ideas. With naru, it expresses change. With no extra particle, it can work adverbially.

• 赤くてきれいです。 [Akakute kirei desu.] = It is red and pretty.
• 部屋が広くなる。 [Heya ga hiroku naru.] = The room becomes spacious.
• 早く起きる。 [Hayaku okiru.] = To wake up early.

Conditional and descriptive extensions

The conditional ending -kereba is common in written Japanese and polite explanations:

• 安ければ買います。 [Yasukereba kaimasu.] = If it is cheap, I will buy it.

You will also see extensions such as -sou for appearance and -sugiru for excess:

• おいしそう = looks delicious
• 難しすぎる = too difficult

The main exception: ii and yoi

The adjective for good is a classic exception. In plain present speech, Japanese often uses ii [いい]. But when the word conjugates, it usually goes back to the older stem yoi [良い].

Form	Correct Japanese	Meaning
Present	いい	good
Negative	よくない	not good
Past	よかった	was good
Past negative	よくなかった	was not good

The same logic appears in compounds such as kakkoii [かっこいい]. Its negative form is kakkoyokunai [かっこよくない], not kakkoiikunai.

Useful example sentences with i-adjectives

• この映画は面白いです。 [Kono eiga wa omoshiroi desu.] = This movie is interesting.
• 昨日は忙しかったです。 [Kinou wa isogashikatta desu.] = Yesterday was busy.
• そのカレーは辛くないです。 [Sono karee wa karakunai desu.] = That curry is not spicy.
• 空が青くてきれいです。 [Sora ga aokute kirei desu.] = The sky is blue and beautiful.
• このかばんは高すぎます。 [Kono kaban wa takasugimasu.] = This bag is too expensive.
• 時間があれば、新しい本を読みます。 [Jikan ga areba, atarashii hon o yomimasu.] = If I have time, I will read a new book.

Common Japanese i-adjectives to memorize

Memorizing useful pairs helps you understand both meaning and contrast. The list below focuses on frequent adjectives that appear in conversation, lessons, and reading practice.

Japanese	Reading	Meaning
新しい	atarashii	new
古い	furui	old
大きい	ookii	big
小さい	chiisai	small
高い	takai	expensive, tall
安い	yasui	cheap
暑い	atsui	hot weather
寒い	samui	cold weather
熱い	atsui	hot to the touch
冷たい	tsumetai	cold to the touch
早い	hayai	early
速い	hayai	fast
白い	shiroi	white
黒い	kuroi	black
赤い	akai	red
青い	aoi	blue
甘い	amai	sweet
辛い	karai	spicy
面白い	omoshiroi	interesting
難しい	muzukashii	difficult
優しい	yasashii	kind, gentle
忙しい	isogashii	busy
楽しい	tanoshii	fun
悲しい	kanashii	sad
嬉しい	ureshii	happy, glad
怖い	kowai	scary
かわいい	kawaii	cute
欲しい	hoshii	wanted, desired

If you want more vocabulary practice after these basics, our N4 and N5 adjective list gives you a broader set of words to review in context.

Final notes for learners

The fastest way to master i-adjectives is to stop treating them as a long list of abstract rules. Learn a few high-frequency adjectives, use them in short sentences, and repeat the same core transformations until they feel automatic: takai, takakunai, takakatta, takakunakatta.

Once those patterns feel natural, you will start recognizing the same logic in hundreds of other words. That is when Japanese adjective conjugation becomes much easier to read, hear, and use in real conversation.