LESSON NOTES · レッスンノート

N4Lesson notes · Sep 30, 2026

Important in Japanese: 大事だいじ, 大切たいせつ, 重要じゅうよう — three words, three temperatures

"Important" in Japanese is 大事だいじ (daiji) in everyday talk, 大切たいせつ (taisetsu) when feelings are involved, and 重要じゅうよう (juuyou) in writing and business — and all three are な-adjectives.

Dictionaries give you all three as "important" and leave it there. That is why learners freeze: which one do you say to a friend, which one goes in an email, and which one do you use when you mean "someone I care about"? The meaning barely changes between them. The temperature does.

The basics

What is the difference between 大事だいじ, 大切たいせつ, and 重要じゅうよう?

Think of them on a dial. 重要じゅうよう is cold and official, 大事だいじ is room temperature and everywhere, 大切たいせつ is warm.

Word Reading Hardness Feeling in it? Typical home
大事だいじ だいじ Casual to neutral A little Everyday conversation, the most common of the three
大切たいせつ たいせつ Neutral, a bit gentle Yes, strongly People, memories, objects you treasure
重要じゅうよう じゅうよう Hard, formal No News, business, notices, documents
肝心かんじん かんじん Neutral to hard No, but pointed "The crucial part" of something

If you only want one word for the next month, take 大事だいじ. It is the safest in speech, and nobody will blink.

これは大事だいじな話はなしです。 — This is an important conversation. (neutral, spoken) 大事だいじなことなので、もう一度いちど言いいます。 — It's important, so I'll say it once more. (neutral, a teacher's line)

Why is 大事だいじ so common in conversation?

Because it does the boring, useful job. It means "matters, shouldn't be neglected" without adding emotion or formality. You use it for deadlines, advice, health, and plans, the way English uses "important" and "a big deal."

明日あしたの会議かいぎ、大事だいじだから遅おくれないでね。 — Tomorrow's meeting is important, so don't be late. (casual-polite, between coworkers) 睡眠すいみんは大事だいじだよ。 — Sleep matters. (casual, friendly advice)

One more thing 大事だいじ owns: お大事だいじに ("please take care of yourself"). It is what you say to someone who is sick or injured, the Japanese "get well soon." If you want the vocabulary around being ill, how to say sick in Japanese covers it.

風邪かぜですか。お大事だいじに。 — You have a cold? Get well soon. (polite, said at the end of a conversation)

When do you use 大切たいせつ instead?

When the thing is precious to someone. 大切たいせつ carries warmth, so it fits people, relationships, time, memories, and objects you would not throw away. Its verb form, 大切たいせつにする, means "to cherish, to treat with care."

家族かぞくは私わたしにとって一番大切いちばんたいせつな人ひとです。 — My family are the most important people in my life. (polite, sincere) この本ほんは祖父そふからもらった大切たいせつなものです。 — This book is precious to me; my grandfather gave it to me. (polite, personal) 時間じかんを大切たいせつにしてください。 — Please treat your time as precious. (polite, encouraging)

Notice that 私わたしにとって shows up in the first example. That is the natural partner of 大切たいせつ: you are giving whose point of view the "importance" comes from. The full story is in 〜にとって, and it is worth a quick look because it works with all three words here.

And where does 重要じゅうよう live?

In places where you would not say "important" out loud with a shrug: news, official notices, reports, meetings run in a suit. 重要じゅうよう is heavy. It says "this is significant" without saying anything about how anyone feels.

重要じゅうようなお知しらせがあります。 — We have an important announcement. (formal, notices and email subject lines) これは非常ひじょうに重要じゅうような問題もんだいです。 — This is a very important issue. (formal, business or news) 重要事項じゅうようじこうをご確認かくにんください。 — Please confirm the important points. (formal, documents, contracts)

You can say 重要じゅうよう to a friend, but it sounds like you are reading the news. It is a register choice, the same split you meet in written vs spoken Japanese.

Beyond the basics

What is 肝心かんじん for?

肝心かんじん (かんじん) means "the crucial, key part" — the part everything hangs on. English would say "crucial," "the main point," or "when it really counts." It is almost always used as 肝心かんじんな〜 or 肝心かんじんの〜, and it often appears in complaints about the moment that goes wrong.

肝心かんじんなところで忘わすれてしまった。 — I forgot at the most crucial moment. (casual-neutral, regret) 肝心かんじんの名前なまえが思い出おもいだせない。 — I can't remember the one name that matters. (casual, frustration) 何事なにごとも最初さいしょが肝心かんじんです。 — The beginning is crucial in everything. (polite, a proverb-like line)

The other three describe how much something matters. 肝心かんじん picks out which part matters. That is why "the important thing is..." often turns into 肝心かんじんなのは〜 when the speaker wants to point at the core.

How do you say "it is important to..."?

Use a verb in the plain form plus ことが大事だいじだ (or 大切たいせつだ, or 重要じゅうようだ). The こと turns the verb into a noun, so the whole sentence can take a な-adjective.

毎日まいにち少すこしずつ続つづけることが大事だいじです。 — It's important to keep going a little every day. (polite, study advice) 人ひとの話はなしを最後さいごまで聞きくことが大切たいせつだ。 — It's important to listen to people to the end. (neutral, a lesson or moral) 早はやく報告ほうこくすることが重要じゅうようです。 — Reporting early is important. (formal, workplace)

Which こと do you need, and why not の? Both can nominalize, but ことが大事だいじだ is the standard, slightly firmer choice for advice and principles. The choice is explained in こと vs の.

A negative version works the same way: 〜ないことが大事だいじ ("it is important not to...").

焦あせらないことが大事だいじだよ。 — The key is not to panic. (casual, a reassuring tip)

Are these all な-adjectives?

Yes, all of them. 大事だいじ, 大切たいせつ, 重要じゅうよう, and 肝心かんじん need な before a noun and だ or です at the end, so 大事だいじな話はなし, 重要じゅうようなお知しらせ, 大切たいせつな人ひと.

大切たいせつな人ひと — an important person to me (な before a noun) この資料しりょうは重要じゅうようだ。 — These materials are important. (plain form, ends in だ)

They are not い-adjectives, so 大事だいじい or 重要じゅうようくない will not work. The negative is 大事だいじじゃない. If that split is still fuzzy, see い-adjectives vs な-adjectives.

Can 大事だいじ do things the others cannot?

Two small ones. First, 大事だいじにする is very close to 大切たいせつにする, so "take care of your health" can be 体からだを大事だいじに or 体からだを大切たいせつに. Second, 大事だいじ can be read おおごと and means "a big deal, a serious affair," as in 大事だいじになる, "it turned into a big deal." The kanji are the same, the reading and meaning are not, so notice which reading the context asks for.

How does this sound in anime?

Anime loves 大切たいせつ. Look for 大切たいせつな人ひと and 大切たいせつなもの ("something precious") in emotional scenes, where a character says what they are fighting for. Compare a coach or friend telling someone 大事だいじだぞ, which is an instruction, not a confession. 重要じゅうよう is more likely from a commander, a scientist, or an announcement over the speaker. Once you hear the temperature, a character's tone is mostly decided before they finish the sentence.

Common mistakes

  • Using 重要じゅうよう for people. 重要じゅうような人ひと is possible in business ("a key person"), but it sounds like a rank, not affection. For "someone important to me," use 大切たいせつな人ひと.
  • Saying お大切たいせつに to someone who is sick. The set phrase is お大事だいじに. It is fixed, like "bless you."
  • Using 重要じゅうよう in casual chat. Your friend asked if the party matters, and you answer 重要じゅうようです. It sounds like a legal document. Use 大事だいじ.
  • Forgetting な. 大事だいじ話はなし is wrong; it is 大事だいじな話はなし.
  • Confusing 大事だいじ the adjective with おおごと. In 大事だいじになった, the word is not "important," it is "a big deal happened."
  • Treating 肝心かんじん as a general "important." 肝心かんじんな天気てんき is odd. 肝心かんじん needs a "crux": the part that decides everything.

FAQ

What is the most common way to say important in Japanese? 大事だいじ is the most common in conversation. In writing and business you will see 重要じゅうよう far more often. Both are fine, but they sit at different registers.

Is 大事だいじ or 大切たいせつ more polite? Neither is more polite, they are both neutral. 大切たいせつ sounds a bit warmer and more sincere. If you want formality, that is 重要じゅうよう, not 大切たいせつ.

What does お大事だいじに mean? It is what you say to someone who is ill or hurt: "take care, get well soon." It is a fixed phrase that uses 大事だいじ. Do not swap in 大切たいせつ.

Can I say 大事だいじ to mean "important person"? Yes: 大事だいじな人ひと works, and it is common. 大切たいせつな人ひと leans more sentimental. In a love story or a farewell scene, you will hear 大切たいせつ more often.

How do you say "the important thing is..."? Say 大事だいじなのは〜 or 大切たいせつなのは〜, or 肝心かんじんなのは〜 if it is the core of the matter. Follow it with a noun or a clause ending in こと: 大事だいじなのは、続つづけることです。

Practice

Build each answer before opening it. Questions 3 and 4 are a pair, and so are 7 and 8.

1. You want to tell a sick friend to get well soon. What do you say?

Show answer

お大事だいじに — it is a fixed phrase built on 大事だいじ. お大切たいせつに is not used.

2. You are writing "We have an important announcement" on a company notice. Which word fits best?

Show answer

重要じゅうようなお知しらせ — formal written notices use 重要じゅうよう, which carries no personal feeling.

3. Say "My family is important to me" with warmth.

Show answer

家族かぞくは私わたしにとって大切たいせつです — 大切たいせつ carries affection, and にとって gives the point of view.

4. Say "This meeting is important, so don't be late" to a coworker, in ordinary speech.

Show answer

この会議かいぎは大事だいじだから遅おくれないでね — 大事だいじ is the neutral spoken word. 大切たいせつ would sound oddly tender, and 重要じゅうよう oddly stiff.

5. Which is correct: 大事だいじ話はなし or 大事だいじな話はなし?

Show answer

大事だいじな話はなし — 大事だいじ is a な-adjective, so it needs な before a noun.

6. Say "It is important to study every day" using ことが.

Show answer

毎日まいにち勉強べんきょうすることが大事だいじです — the verb in plain form plus こと turns it into a noun, so it can take 大事だいじです.

7. "I forgot at the crucial moment." Which word points to the crux?

Show answer

肝心かんじんなところで忘わすれてしまった — 肝心かんじん marks the part everything depends on, not general importance.

8. Why would 肝心かんじんな人ひと not be natural for "someone I care about"?

Show answer

肝心かんじん points at the crux, not at feeling. For someone you care about, use 大切たいせつな人ひと or 大事だいじな人ひと.

9. How do you say "it is important not to panic"?

Show answer

焦あせらないことが大事だいじです — the negative plain form 焦あせらない plus ことが大事だいじ.

Use a trial lesson to choose between 大事だいじ, 大切たいせつ and 重要じゅうよう for a person, a keepsake and a deadline, and wish someone お大事だいじに.

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.

大事	だいじ — important, valuable
お大事に	おだいじに — get well soon, take care
大切	たいせつ — important, precious
大切にする	たいせつにする — to cherish, to take care of
重要	じゅうよう — important, significant (formal)
肝心	かんじん — crucial, essential
お知らせ	おしらせ — announcement, notice
問題	もんだい — problem, issue
家族	かぞく — family
睡眠	すいみん — sleep
焦る	あせる — to panic, to be impatient
大事	おおごと — a serious matter, a big deal

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, and the 大事だいじ versus 大切たいせつ question comes up in lessons all the time. 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 · N4 · Read something at this level: JLPT N4 stories with audio

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