LESSON NOTES · レッスンノート

N5Lesson notes · Oct 2, 2026

Smart in Japanese: 頭あたまがいい, 賢かしこい, and which one to say

"Smart" in Japanese is most often 頭あたまがいい (atama ga ii), literally "the head is good" — but 賢かしこい (kashikoi), 頭あたまが切きれる, 優秀ゆうしゅう and 天才てんさい each describe a different kind of smart, and スマート does not mean smart at all.

If you search "smart in japanese hiragana", the answer is あたまがいい and かしこい. But English "smart" covers a lot of ground: good at school, quick in a conversation, clever with a plan, well-behaved for a dog. Japanese splits those jobs between several words, and picking the right one is the whole skill.

The basics

How do you say "smart" in Japanese?

The default is 頭あたまがいい (あたまがいい). It describes someone who is intelligent in a general, everyday way: good at studying, quick to understand, hard to fool.

あの人ひとは頭あたまがいいですね。 — That person is smart, isn't he/she? (polite, a plain compliment) 姉あねは頭あたまがいいです。 — My older sister is smart. (polite, describing family)

Notice the grammar. 頭あたま is the topic of the quality, and いい is the adjective, so the pattern is [person] は 頭あたまが いい. You are saying "as for this person, the head is good." It sounds odd in English, but it is the same structure Japanese uses for body-part descriptions, and it works for almost every kind of "smart" you will need to say.

What happens when you put 頭あたまがいい in the past or negative?

This is the trap. いい is the one adjective that changes its stem: いい becomes よ before かった and くない. So the past is 頭あたまがよかった, not 頭あたまがいかった, and the negative is 頭あたまがよくない.

彼かれは子こどものころ、頭あたまがよかったです。 — He was smart as a child. (polite, past) 私わたしは頭あたまがよくないです。 — I'm not smart. (polite, negative, self-description)

The same rule applies to any word built on いい, which is why it is worth learning once. The full conjugation pattern is in Japanese adjective past tense.

What does 賢かしこい mean, and how is it different?

賢かしこい (かしこい) means wise, clever, or sensible. It leans toward good judgment rather than raw intelligence. A person who saves money, avoids a mistake, or chooses the sensible option is 賢かしこい.

それは賢かしこい選択せんたくですね。 — That's a smart choice, isn't it? (polite, praising a decision) この犬いぬは本当ほんとうに賢かしこいですね。 — This dog is really smart. (polite, about a pet) 賢かしこいね! — Good thinking! / Aren't you clever! (casual, to a child or friend)

Where 頭あたまがいい describes what a person is, 賢かしこい often describes what they did. It is also the normal word for animals and young children, who are praised for understanding something rather than for academic ability.

Quick comparison

Word Reading Best meaning Typical situation
頭あたまがいい あたまがいい intelligent, bright school, general ability
賢かしこい かしこい wise, clever decisions, pets, children
頭あたまが切きれる あたまがきれる sharp, quick-witted business, arguments
優秀ゆうしゅう ゆうしゅう excellent, high-performing work, grades, evaluations
天才てんさい てんさい genius exaggerated praise or real talent
物知ものしり ものしり knowledgeable someone who knows many facts
利口りこう りこう clever, well-behaved children, older style

Beyond the basics

What does 頭あたまが切きれる mean?

頭あたまが切きれる (あたまがきれる) is "the head cuts," meaning sharp. It describes someone who sees the point instantly, spots the flaw in an argument, or solves a problem faster than everyone else. It has a slightly cool edge, closer to "razor sharp" than "kind and bright."

あの課長かちょうは頭あたまが切きれる人ひとだ。 — That section chief is a sharp person. (neutral, written/spoken, about a coworker) 彼女かのじょは頭あたまが切きれるから、うそはすぐばれるよ。 — She's sharp, so lies get found out right away. (casual, warning)

It is a respectful word, but it can also carry a hint of "careful around this person," so it fits business and strategy more than a cozy compliment.

What is the difference between 優秀ゆうしゅう and 頭あたまがいい?

優秀ゆうしゅう (ゆうしゅう) is an evaluation of results: excellent, top-performing. It does not say whether someone is naturally intelligent; it says that their output is high quality. That makes it the word of workplaces, schools and reports.

優秀ゆうしゅうな学生がくせいですね。 — He/She is an excellent student. (polite, teacher talking) 彼かれは新人しんじんなのに、とても優秀ゆうしゅうだ。 — Even though he's new, he's very capable. (neutral, evaluating a coworker)

You would not say 優秀ゆうしゅう to a friend in a casual chat; it sounds like a performance review. 頭あたまがいい is personal and warm; 優秀ゆうしゅう is official.

What about 物知ものしり, 利口りこう, and 天才てんさい?

Three more words that cover specific corners of "smart":

  • 物知ものしり (ものしり): someone who knows a lot of facts. The "walking encyclopedia." 物知ものしりだね is a friendly compliment for a person with lots of trivia.
  • 利口りこう (りこう): clever or well-behaved. It sounds a little old-fashioned for adults, but it is still used for children and animals. お利口りこうさん is what adults say to a child who is sitting quietly or following instructions.
  • 天才てんさい (てんさい): genius. Real geniuses exist, but the word is also used loosely, as a joke or a big compliment.

物知ものしりだね!なんでも知しってるね。 — You know so much! You know everything. (casual, impressed) お利口りこうさんにしてたね。 — You were such a good kid. (casual, adult to a child, praising behavior) この問題もんだいが解とけるなんて、天才てんさいだね! — You can solve this problem? You're a genius! (casual, exaggerated praise)

Calling a toddler or a dog お利口りこうさん is warm. Calling a coworker 利口りこう would sound like you are patting them on the head.

Does スマート mean smart in Japanese?

No. スマート is a loanword that Japanese took from English "smart" and then changed. In Japanese it means slim, stylish, or neat, and almost never "intelligent."

彼かれはスマートな体型たいけいだ。 — He has a slim build. (neutral, about appearance) スマートな着つこなしですね。 — That's a sharp, stylish way of dressing. (polite, complimenting an outfit)

If you tell someone "あなたはスマートですね", they will probably hear "you're slim" or "you're stylish." This is a classic wasei-eigo trap; more like it are in wasei-eigo: English words that aren't. The one place スマート means something smart-like is in compound words such as スマートフォン (smartphone) and スマートウォッチ, where it means "connected" or "high-tech."

Can 頭あたまいいね sound sarcastic?

Yes. The words are positive, but tone controls everything. Said flatly, with a drop at the end, or after someone has just made an obvious mistake, 頭あたまいいね can be a jab: "Real brilliant, huh."

頭あたまいいね! — You're smart! (casual, warm, rising tone) …頭あたまいいね。 — …Real smart. (casual, flat, sarcastic, after someone's bad idea)

A genuine compliment usually has a smile, a rising pitch, and a reason: 頭あたまいいね、どうやって思おもいついたの? ("You're smart. How did you come up with that?"). The reason is what keeps it from sounding like a joke. For more on how Japanese sarcasm is delivered, see Japanese sarcasm.

How do you respond when someone calls you smart?

Japanese etiquette favors humility. The standard reply is a polite denial.

そんなことないです。 — Not at all. (polite, humble) いえいえ、全然ぜんぜんです。 — No, no, not at all. (polite, casual-polite) ありがとうございます。まだまだです。 — Thank you. I still have a long way to go. (polite, humble but grateful)

Accepting the praise directly with "Yes, I am smart" sounds boastful. The denial is not a literal claim that you are not smart; it is a ritual reply. If you want to be warm and modest at the same time, add ありがとう.

How does "smart" sound in anime?

In anime, intelligence is dramatic. Characters call each other a genius, say a plan is sharp, or marvel at a brain.

天才てんさいか! — Are you a genius or what?! (casual, comic exaggeration, said to a friend who just solved something) こいつ、頭あたまが切きれるぞ。 — This guy is sharp. (casual, a rival being cautious) 頭あたまいい! — So smart! (casual, dropping the particle and だ)

天才てんさいか! is worth memorizing. It is not a literal question; it is a joke-compliment, like saying "genius!" with a laugh. You will hear it in comedy, school stories, and any show where one character does something impressive. The opposite of that impressive character is the all-brawn type called 脳のう筋きん (のうきん), short for 脳のうみそまで筋肉きんにく, "muscles all the way to the brain", and brain in Japanese notes it is a tease, never a compliment.

Common mistakes

  • Saying 頭あたまがいかった. The past of 頭あたまがいい is 頭あたまがよかった. The same applies to よくない and よくて.
  • Using スマート as "intelligent." Native speakers will hear "slim" or "stylish," not "smart."
  • Calling an adult 利口りこう as a compliment. It sounds like praising a child. For adults, use 頭あたまがいい or 優秀ゆうしゅう.
  • Using 優秀ゆうしゅう in casual praise. "あなたは優秀ゆうしゅうですね" can sound like a manager evaluating someone. For friends, 頭あたまいいね is natural.
  • Using 頭あたまいいね without checking the tone. Without a rising pitch and a reason, it can sound sarcastic.

Practice

Try to answer before opening each one. Questions 3 and 4 are a pair, and so are 5 and 6.

1. What is the most common way to say "smart" in Japanese?

Show answer

頭あたまがいい (あたまがいい) — literally "the head is good," used for general intelligence.

2. Say "He was smart as a child" using 頭あたまがいい.

Show answer

彼かれは子こどものころ、頭あたまがよかったです — いい changes to よ before かった, so 頭あたまがいかった is wrong.

3. Say "I'm not smart."

Show answer

私わたしは頭あたまがよくないです — いい becomes よ before くない. This is the negative half of the pair with question 4.

4. Which is right: 頭あたまがいくない or 頭あたまがよくない?

Show answer

頭あたまがよくない — the stem of いい is よ in the negative, so いくない does not exist.

5. You want to praise a dog for being clever. Which word fits best, 賢かしこい or 優秀ゆうしゅう?

Show answer

賢かしこい — it means clever or sensible and is the normal word for pets and children. 優秀ゆうしゅう sounds like a performance review.

6. A manager is writing an evaluation of a new employee who produces excellent work. 賢かしこい or 優秀ゆうしゅう?

Show answer

優秀ゆうしゅう — it evaluates results and belongs in workplaces and reports. This is the pair to question 5.

7. What does 頭あたまが切きれる describe, and how does it feel compared with 頭あたまがいい?

Show answer

Sharp, quick-witted — someone who sees the point instantly. It has a cooler edge than 頭あたまがいい, which is warm and general.

8. Your friend says あなたはスマートですね. What is probably being said about you?

Show answer

You're slim or stylish — スマート is wasei-eigo and does not mean intelligent.

9. Someone praises you with 頭あたまいいね. Give a natural humble reply.

Show answer

そんなことないです — a ritual denial that keeps you modest. Add ありがとうございます if you want to sound grateful too.

10. When can 頭あたまいいね sound sarcastic?

Show answer

When it is flat and follows an obvious mistake — tone and context turn the praise into a jab. A rising pitch plus a reason keeps it sincere.

A trial lesson is a good place to describe a clever friend, a sharp colleague and a genius character, choosing between 頭あたまがいい, 頭あたまが切きれる and 天才てんさい.

FAQ

What is "smart" in Japanese hiragana? The most common words are あたまがいい (頭あたまがいい) and かしこい (賢かしこい). Both are written in kanji in normal text, but hiragana is fine for learners and for children's books.

What is "smart" in Japanese language for a person who dresses well? That is スマート or おしゃれ. Both describe style, not intelligence. For someone who is smart and stylish, you can say 頭あたまがよくておしゃれ.

Is 頭あたまがいい polite enough for a teacher or boss? It is not rude, but praising a superior's intelligence directly can sound presumptuous. Safer options are 優秀ゆうしゅうですね or すごいですね, or a specific compliment about their work.

What is "smart" in Japanese name or as a nickname? There is no everyday nickname meaning "smart." Names with 賢さとし (さとし, けん) or 智さとる (さとし, とも) use kanji for wisdom, but that is naming, not a casual word. Calling someone 天才てんさい as a friendly nickname is a joke rather than a formal title.

Can 賢かしこい describe a person's appearance or behavior? It describes behavior and judgment, not appearance. A sensible choice is 賢かしこい. A good-looking outfit is おしゃれ or スマート.

Is 頭あたまがいい the same as 勉強べんきょうができる? Not exactly. 勉強べんきょうができる means "good at studying" (a skill at school). 頭あたまがいい is broader: it includes quick thinking and understanding. Someone can be 頭あたまがいい without getting top grades.

For how to say the opposite, see stupid in Japanese: baka, aho and friends. If you want more adjectives for describing people, Japanese personality adjectives covers the common ones, and good at and bad at in Japanese shows how to talk about skills.

Vocabulary from this article

Tap the block to select all of it, then copy. In Anki: File → Import, note type Basic, separator Tab — the first column becomes the front, the second the back.

頭がいい	あたまがいい — smart, intelligent
賢い	かしこい — wise, clever
頭が切れる	あたまがきれる — sharp, quick-witted
優秀	ゆうしゅう — excellent, high-performing
天才	てんさい — genius
物知り	ものしり — someone who knows a lot
利口	りこう — clever, well-behaved
お利口さん	おりこうさん — good boy/girl (to a child)
スマート	スマート — slim, stylish
そんなことないです	そんなことないです — not at all (humble reply)
勉強ができる	べんきょうができる — good at studying

I'm Yuuki, a Japanese teacher based in Tokyo. I've taught on italki as a Top 1% teacher and watched over 1,500 anime, so most of the example sentences on this blog come from lines I've actually heard students ask about — including this one, which comes up whenever learners want to compliment someone. For practice with feedback, Book a trial lesson · $13, or work through Japanese practice exercises first.

Sources: the author's own lessons and standard reference grammars.

More drills like the ones above, plus a timed JLPT-style mock test: Practice · N5 · Read something at this level: JLPT N5 stories with audio

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