“〜totan (ni)”: The Moment 〜, Instantly (instantaneous connection) [JLPT N3]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

「ベッドに入ったとたん眠った」 — one action ends and, out of nowhere, the next hits.

「ドアを開けたとたん、猫が飛び出した」 — at that very instant, suddenly …

「ドアを開けたとたん、猫が飛び出した」 (the instant I opened the door, a cat shot out) — 「〜とたん（に）」 expresses “the moment (I finished) …, (instantly) …”: at the very instant the prior action completes, the next thing happens suddenly, unexpectedly. This guide covers 「とたん」's attachment and feel, separating it from the literary 「や否や・が早いか」 and the colloquial 「と／たら」.

Core: the moment (I finish) ～, (instantly, suddenly) ～

「verb た-form ＋ とたん（に）」 = “the moment ～, (instantly) …” — the prior action just completes, and the second clause happens right after, suddenly:

• 立ち上がったとたん、めまいがした (the moment I stood up, I got dizzy).
• 家を出たとたん、雨が降り出した (the moment I left home, it started raining).

Feel: “no sooner … than (suddenly) …” — the core is “at the instant the prior action completes, the second clause abruptly occurs,” where the second clause is usually an unforeseeable change beyond the speaker's will (rain, dizziness, a cat shooting out). It carries surprise.

Attachment & second-clause traits

See it in context

• ベッドに入ったとたん、ぐっすり眠ってしまった。(The moment I got into bed, I fell fast asleep.)
• 彼の顔を見たとたん、涙があふれた。(The moment I saw his face, tears overflowed.)
• 電気を消したとたん、雷が鳴った。(The moment I turned off the light, thunder struck.)
• 立ち上がったとたんに、足がしびれて転んだ。(The moment I stood up, my leg went numb and I fell.)
• 春になったとたん、花が一斉に咲き始めた。(The moment spring came, the flowers all began to bloom at once.)

⚠️ Common mistakes to avoid

① Always attaches to the ‘verb た-form,' and the second clause takes no will/command. Before 「とたん」 must be a verb た-form (開けたとたん, not 開けるとたん); the second clause can only be a sudden, unexpected, non-volitional event (rain, falling, a cat shooting out), and takes no will, command, or request (×ドアを開けたとたん、入ってください). For a request/will “after doing A, (please/I'll) do B,” use 「たら」 (開けたら入ってください = come in once it's open). This is 「とたん」's key difference from 「たら」.

② 「とたん」 carries surprise, 「と／たら」 are more neutral. All three can mean “no sooner … than …,” but とたん specifically stresses ‘instant ＋ surprise' (座ったとたん、椅子が壊れた = the moment I sat, the chair broke, a sudden mishap); 「と」 leans inevitable, regular linkage (ボタンを押すと開く = press and it opens, a mechanical inevitability); 「たら」 leans general condition or discovery. To stress “no sooner … than, unexpectedly suddenly …” use とたん.

③ Most natural when the two clauses are ‘different subjects or non-volitional.' 「とたん」's second clause is often a different subject, or something beyond the speaker's control (opened (I) → a cat shot out (cat); stood (I) → got dizzy (a physical reaction)). If both clauses are the same person's consecutive intentional actions (wake up → brush teeth), 「とたん」 is unnatural; for “do A then do B,” 「〜てから／〜たら」 is better. とたん is specifically “no sooner …, than (unexpectedly) suddenly ….”

🔄 Compare with similar forms: とたん／や否や・が早いか／と／たら

💡 How to remember this

「〜とたん（に）」 = the moment (I finish) ～, (instantly, suddenly) …, its core “at the instant the prior action completes, the second clause abruptly, unexpectedly occurs” (ドアを開けたとたん、猫が飛び出した). Three points: ① fixed attachment — always the verb た-form ＋ とたん; ② the second clause is a sudden, unexpected, non-volitional change — no will/command/request (that takes 「たら」, 開けたら入って); ③ it carries surprise, unlike the neutral 「と／たら」. To vividly depict the instant surprise of “no sooner …, than suddenly …” (usually natural, beyond one's control), とたん is the most vivid. If the two clauses are the same person's consecutive intentional actions, or a request follows, use 「〜てから／〜たら」.

❓ FAQ

Q: 「とたん」 and 「たら」 both mean ‘no sooner … than …' — what's the difference?

Whether the second clause can take a will/command, and whether there's a ‘surprise' flavor. 「〜たとたん」 = the moment (I finish) … (the second clause is an unforeseeable, non-volitional abrupt change, with surprise): 窓を開けたとたん、強い風が吹き込んだ (the moment I opened the window, a strong wind blew in — a sudden, unwilled surprise). Its second clause can only be a natural, unexpected event, never a command, request, or will (can't say 「開けたとたん、入ってください」). 「〜たら」 = after doing … (the second clause freely takes will, command, request, or a chance discovery, more neutral): 窓を開けたら、換気してください (after opening the window, please ventilate — a request, ○); 窓を開けたら、外は雪だった (I opened the window, and it was snowing outside — a chance discovery, ○). Test: if the follow-up is ‘a sudden, unexpected, non-volitional change' → とたん; if it takes ‘a request/command/will' or is just plain sequence → たら. E.g., 「ドアを開けたとたん、犬が飛び出した」 (the moment I opened the door, a dog shot out — surprise); but 「ドアを開けたら、閉めてください」 (once you open the door, please close it — a request, only たら works). One is “instant surprise,” one takes “a following action-command.”

Q: How does 「とたん」 differ from the literary 「や否や・が早いか」?

Close in meaning (both “the instant … then …”), differing in register and the second clause's nature. 「〜とたん（に）」 = no sooner ～ than (instant ＋ surprise), colloquial-to-general, the second clause usually a ‘non-volitional, unexpected' change: ベルが鳴ったとたん、みんな席を立った (no sooner did the bell ring than everyone stood up). Usable in daily conversation and general writing, its second clause leaning “natural, sudden.” 「〜や否や」「〜が早いか」 = the instant ～ then …, more literary, written, stiff, stressing ‘almost simultaneous, right after,' the second clause often ‘an intentional, swift action': 彼は教室に入るや否や、大声で叫んだ (the instant he entered the classroom, he shouted — written, an intentional action); ベルが鳴るが早いか、生徒たちは教室を飛び出した (no sooner did the bell ring than the students dashed out — literary, a swift intentional action). These two appear more in novels and written description, stiff and dramatic. Test: everyday, natural sudden second clause → とたん; written/literary, stressing an immediate swift action → や否や・が早いか. Attachment differs too: とたん takes the た-form (入ったとたん), while や否や・が早いか take the dictionary form (入るや否や・入るが早いか) — don't attach them wrong.

🖊️ Practice Quiz

Q1. 「ベッドに入っ___とたん、眠ってしまった。」(fell asleep the moment I lay down)

(A) て　(B) た　(C) る　(D) ている

Q2. 「学校を卒業し___とたん、仕事が見つかった。」(found a job right after graduating)

(A) て　(B) た　(C) る　(D) ている

Q3. 「窓を開け___とたん、強い風が入ってきた。」(the moment I opened the window, strong wind came in)

(A) て　(B) る　(C) た　(D) ていた

Q4. Which uses とたん correctly?

(A) 家に帰るとたん、ご飯を食べた。

(B) 家に帰ったとたん、電話が鳴った。

(C) 家に帰ってとたん、ご飯を食べた。

(D) 家に帰ったとたん、ご飯を食べようと思った。

Q5. 「起き___とたん、頭痛がした。」(the moment I woke, my head hurt)

(A) て　(B) る　(C) た　(D) ていた

Answer Key

1. (B) た ── とたん always attaches to the verb ta-form: 入ったとたん.

2. (B) た ── 卒業したとたん (right after graduating).

3. (C) た ── 開けたとたん (the moment I opened it).

4. (B) 家に帰ったとたん、電話が鳴った ── ta-form ＋ とたん, with an unexpected event in the latter (not a volitional/intentional action).

5. (C) た ── 起きたとたん (the moment I woke up).