The Difference Between きれい (kirei) vs 美しい (utsukushii)｜Japanese Grammar (N5–N3)

When you see a flower, you say “きれい (kirei)!” When you clean your room, you also say “きれい (kirei)!”

But there is another word for “beautiful”: 美しい (utsukushii). When should you use it?

きれい (Kirei) is a very useful, everyday word for “pretty” and “clean.”
美しい (Utsukushii) is a formal, artistic word for “beautiful” or “magnificent.”

This article will explain the important differences in meaning and grammar (Adjective types!).

Usage Explanation ①: きれい (kirei) – “Pretty” & “Clean”

きれい (kirei) is a na-adjective (Warning: it ends in ‘i’, but it is ‘na’!). It is used in daily conversation.

It has two main meanings:

Pretty / Beautiful: Pleasing to look at (casual).
Clean / Tidy: Not dirty, organized.

Example 1: (Pretty)

わあ、きれいな 花（はな）ですね。(Wā, kirei na hana desu ne.)

Wow, that is a pretty flower.

Example 2: (Clean)

部屋（へや）を掃除（そうじ）して、きれいにしました。(Heya o sōji shite, kirei ni shimashita.)

I cleaned the room and made it clean.

Example 3: (Grammar Check)

彼女（かのじょ）はきれいでした。(Kanojo wa kirei deshita.)

She was beautiful. (Past tense of Na-adj)

Key Point: Only きれい (kirei) can mean “clean” (no dirt).

Usage Explanation ②: 美しい (utsukushii) – “Beautiful” (Formal)

美しい (utsukushii) is an i-adjective.

It means “beautiful,” “lovely,” or “magnificent.” It describes something that deeply touches your heart or is artistically perfect. It sounds more formal, poetic, and sophisticated than kirei.

Example 1: (Touching beauty)

日本（にほん）の自然（しぜん）は、とても美しいです。(Nihon no shizen wa, totemo utsukushii desu.)

Japan’s nature is very beautiful.

Example 2: (Artistic/Formal)

それは、美しい 音楽（おんがく）でした。(Sore wa, utsukushii ongaku deshita.)

It was a beautiful piece of music.

Example 3: (Grammar Check)

月（つき）が美しかったです。(Tsuki ga utsukushikatta desu.)

The moon was beautiful. (Past tense of i-adj)

Key Point: 美しい (utsukushii) is for high-level beauty. It is never used for “cleaning a room.”

Comparison: きれい vs 美しい

Be careful with the grammar type!

Feature	きれい (kirei)	美しい (utsukushii)
Adjective Type	Na-adjective (きれいな / きれいでした)	i-adjective (美しい / 美しかった)
Meaning 1	Pretty, Beautiful (Appearance)	Beautiful, Magnificent (Deep feeling)
Meaning 2	Clean, Tidy, Neat	(Does not mean clean)
Formality	Casual / Daily Conversation	Formal / Written / Poetic
Example	トイレがきれいだ。 (The toilet is clean.)	心が美しい。 (Has a beautiful heart.)

Common Mistake Examples

Mistake 1: “I cleaned my room.”

Wrong:: 部屋（へや）を美しくしました。(Heya o utsukushiku shimashita.)
Correct:: 部屋（へや）をきれいにしました。(Heya o kirei ni shimashita.)
Why?: To talk about removing dirt or organizing things (“clean”), you must use きれい. 美しい sounds like you decorated the room like an art museum.

Mistake 2: Past tense grammar

Wrong:: あの花（はな）は、きれいかったです。(Ano hana wa, kireikatta desu.)
Correct:: あの花（はな）は、きれいでした。(Ano hana wa, kirei deshita.)
Why?: This is a very common mistake! きれい ends in “i”, but it is a Na-adjective. It conjugates like a noun (deshita), not an i-adjective (katta).

Practice Quiz

Let’s check your understanding! Choose the correct word.

Q1.

手を洗（あら）って、( ) にしましょう。

Let’s wash our hands and make them ( ). (Clean)

美しく (utsukushiku)
きれいに (kirei ni)

Q2.

京都（きょうと）の紅葉（こうよう）は、本当に ( ) ですね。

The autumn leaves in Kyoto are truly ( ). (Deeply moving beauty)

美しい (utsukushii)
きれい (kirei)

(Note: Both are possible, but which emphasizes the moving, formal beauty?)

Q3.

昨日（きのう）の海（うみ）は ( )。

The sea yesterday was pretty.

きれいかった (kireikatta)
きれいでした (kirei deshita)

Quiz Answers

Q1. (b) きれいに – For “clean” (washing hands), always use kirei.

Q2. (a) 美しい – For impressive scenery, 美しい expresses the emotion better (though きれい is also correct in casual speech).

Q3. (b) きれいでした – Watch out for the na-adjective conjugation!

Summary: Key Differences

Remember these simple rules:

きれい (kirei): “Pretty” AND “Clean.” Casual. Na-adjective (Grammar: きれいな / きれいでした).
美しい (utsukushii): “Beautiful” (Artistic/Moving). Formal. I-adjective (Grammar: 美しい / 美しかった).

If you want to say “clean,” always choose きれい!

Frequently Asked Questions (FAQ)

Q1: Which one means “clean”?: A1: Only きれい (kirei) means “clean.” If you clean your room, it becomes “kirei.” 美しい (utsukushii) never means “clean” (free from dirt).
Q2: Is きれい (kirei) an i-adjective or na-adjective?: A2: This is a trick! Even though it ends with “i” (kirei), it is a na-adjective. So you say きれいな人 (kirei na hito) and きれいでした (kirei deshita). 美しい (utsukushii) is a normal i-adjective.
Q3: Can I use 美しい (utsukushii) for a person?: A3: Yes, but it sounds very formal and respectful. It praises their deep beauty or elegance. For everyday conversation, “きれいな人” (pretty/beautiful person) is much more common.