たとたん (ta totan)
～たとたん — “the moment ～”
Pattern
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動詞た形 ＋ とたん(に)、〜ta-form + とたん(に) (開けたとたん, 座ったとたん)
Meaning and connection
The first action is finished and, right at that instant, something else happens. Attach とたん to the ta-form of a verb: ドアを開けたとたん. The result is usually surprising or sudden.
Restrictions
The second part must be something that happened on its own, not a deliberate action by the speaker. A sentence like 家に着いたとたん、手を洗った (a planned action) is unnatural. Do not use it with commands or wishes either. It is also used only for past events.
Difference from ～と / ～たらすぐ
～たとたん focuses on the unexpected surprise of the second event. ～たらすぐ simply means “right after,” and the second action may be intentional.
Examples
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ドアを開（あ）けたとたん、猫（ねこ）が飛（と）び出（だ）した。
Doa o aketa totan, neko ga tobidashita.
The moment I opened the door, the cat jumped out.
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席（せき）に座（すわ）ったとたん、名前（なまえ）を呼（よ）ばれた。
Seki ni suwatta totan, namae o yobareta.
The moment I sat down, my name was called.
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家（いえ）を出（で）たとたん、急（きゅう）に雨（あめ）が降（ふ）り出（だ）した。
Ie o deta totan, kyū ni ame ga furidashita.
The moment I left the house, it suddenly started to rain.
Common mistakes
- The second part cannot be the speaker's own deliberate action, a command or a request.
- It attaches to the ta-form only, not the dictionary form. 開けるとたん is wrong.
More grammar points
- ぶりに ～ぶりに — for the first time in ～ (a period)
- 中（ちゅう） ～中 (ちゅう／じゅう) — during ～, within ～
- ふと ふと — suddenly, on an impulse
- ごとに ～ごとに — every ～, at each ～
- 一度（いちど）に 一度に — all at once
- から〜にかけて ～から～にかけて — from ～ through ～
- にかけて ～から～にかけて — spanning from ～ to ～
- につれて ～につれて — as ～ progresses, ～ changes
- 際（さい）に ～際に — at the time of ～ / when ～
- 最中（さいちゅう）に ～最中に — right in the middle of ～
- しばらく しばらく — for a while
- すでに すでに — already
- たびに ～たびに — “every time ～”
- てはじめて ～てはじめて — “only after ～ing”
- てからでないと ～てからでないと — “not unless ～ first”
- 途中（とちゅう）で/途中（とちゅう）に 途中で／途中に — “on the way / partway through”
- ついに ついに — “finally / in the end”
- うちに ～うちに — “while ～ / before it changes”
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