とうぜん vs. あたりまえ: Why Japanese Learners Make Mistakes?

When something is completely obvious or goes without saying, Japanese speakers reach for 当然とうぜん or 当あたり前まえ. Both mean “of course” or “naturally”, but they are not interchangeable — and mixing them up is a very common mistake among learners. This guide will make the distinction crystal clear.

Yuka

当然 と 当たり前 ってどう違うの？ (What’s the difference between touzen and atarimae?)

Rei

当然 は少し改まった言い方で、副詞・名詞・形容詞として使えるよ。当たり前 はもっと日常的な表現で、副詞としては使えないんだ。 (Touzen is slightly more formal and can act as an adverb, noun, or adjective. Atarimae is more everyday and cannot be used as an adverb.)

At a Glance

当然 (touzen) — “Of Course / Definitely / That’s Totally Obvious”

“当然とうぜん” can function as an adverb (before a verb), a noun, or an adjective. It sounds more formal and carries a slightly stronger, more assertive tone than 当たり前.

Usage examples:

当然とうぜん、私わたしは怒おこる。 (I will definitely get angry.) — correct as adverb

当然とうぜんだよ！ (That’s totally obvious!) — used as noun/predicate

Sample Conversation

Rei

今回こんかい、お前まえが練習れんしゅうをさぼっていたから日本代表にほんだいひょうに選えらばれなかったんだよ！当然とうぜんだよ！ (You’ve been skipping practice, so you weren’t chosen for the national team. That’s only natural!)

Yuka

また、０点てんとってしまった・・・当然とうぜん、お母かあさん怒おこるだろーな。 (I got a zero again… Mum will definitely be mad.) (mata, 0-ten totte shimatta… touzen, okaasan okoru darō na.)

Rei

道みちで拾ひろった財布さいふは交番こうばんに届とどけろよ！当然とうぜんだろ！ (Turn in a wallet you found on the street to the police box! That’s totally obvious!) (touzen darō!)

当たり前 (atarimae) — “Naturally / That’s Obvious / Common Sense”

“当あたり前まえ” is used in a similar way to 当然, but it cannot be used as a standalone adverb before a verb. If you want to use it in that structure, you need to rephrase:
Wrong: 当あたり前まえ、私わたしは怒おこる。
Correct: 私わたしが怒おこるのは当あたり前まえだ。 (It is only natural that I get angry.)

Sample Conversation

Rei

えっ？ラーメンとごはんの組くみ合あわせ？俺おれの実家じっかなら当あたり前まえだけどー・・・ (What? Ramen with rice? That’s perfectly normal in my family home…)

Yuka

試験前しけんまえなのに当あたり前まえのように毎日まいにち１２時間じかんくらい寝ねてるよね？試験しけん、大丈夫だいじょうぶなの？ (You’re sleeping about 12 hours every day as if it’s normal, even before exams. Are you okay?) (atarimae no you ni mainichi jūni jikan kurai ne teru yo ne?)

Yuka

いやいや、二日前ふつかまえは一昨日おとといって当あたり前まえじゃね？ (Come on, isn’t it obvious that 2 days ago is the day before yesterday?) (atarimae jya ne?)

Quick Quiz

Choose 当然 or 当たり前 (or both) for each blank.

Q1. _____ 、彼は怒った。(He was _____ angry.) → Answer: 当然 only (adverb position — 当たり前 cannot be used here)

Q2. 彼が怒るのは _____ だ。(It is _____ that he got angry.) → Answer: Both 当然 and 当たり前 work here

Q3. ルールを守るのは _____ のことだ。(Following the rules is _____.) → Answer: 当たり前 (most natural in this common set phrase)

当然とうぜん and 当あたり前まえ both convey “of course / naturally”, but 当然 is slightly more formal and can function as an adverb before a verb, while 当たり前 is more conversational and cannot. When in doubt in a formal or written setting, 当然 is the safer choice.

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