Explanation
Express the moment something happens; 'as soon as', 'just when'.
Formation
Verb-past + たとたん
Detailed explanation
The ～たとたん grammar point is used to express that an action or event occurred at the same moment another action or event happened. It can be translated as 'as soon as' or 'just when.' It requires the past tense of a verb.
Examples
ドアを開けたとたん、雨が降り始めた。
Doa o aketa totan, ame ga furi-hajimeta.
As soon as I opened the door, it started raining.
電話をかけたとたん、バッテリーが切れた。
Denwa o kaketa totan, batterī ga kireta.
Just when I made the phone call, the battery died.
彼女に会ったとたん、思い出の歌が流れた。
Kanojo ni atta totan, omoide no uta ga nagareta.
No sooner had I met her than a nostalgic song started playing.
テストが終わったとたん、リラックスできた。
Tesuto ga owatta totan, rirakkusu dekita.
The moment the test ended, I was able to relax.
Practice
Grammar content sourced from hanabira.org.