たとたんに

The grammar pattern たとたんに expresses that the very instant one action was completed, another event occurred immediately afterward – often unexpectedly. It translates to "the moment," "the instant," or "just as" in English. The kanji form is とたん途端.

Formation

Attach とたんに directly after a verb in the た-form:

Key nuance: unexpectedness

A defining feature of たとたんに is that the second event is typically unexpected, involuntary, or beyond the speaker's control. It describes something that happened to the speaker or around them – not something they deliberately chose to do next.

Because of this, it would sound unnatural to use たとたんに when the second clause describes a planned or intentional action by the subject. For example, ✗ 家に帰ったとたんに、テレビをつけた would be awkward because turning on the TV is a deliberate action.

に is optional

The particle に can be dropped in casual speech, though it is more commonly included:

Comparison with similar patterns

• ～たら and ～と can also describe sequential events, but they do not carry the same nuance of immediacy and surprise.
• ～や否や (no sooner than) is a more literary equivalent of たとたんに.
• ～たとたんに focuses on a single past event, so it is not used for habitual actions or future events.