SuGoiSuす語彙すGrammar › N2 · 02 Time and sequence
〜や否や: as soon as; the moment
N2 · 02 Time and sequence
Says that something happened immediately after another thing, often something surprising or sudden.
Verb dictionary form + や否や. Written or formal. The second event is usually a reaction and cannot be a request or command. Close to 〜とたん, but 〜や否や is used with the dictionary form and is a bit more literary.
Examples
彼は電話を切るや否や、部屋を飛び出した。
The moment he hung up the phone, he ran out of the room.
ベルが鳴るや否や、客が一斉に入ってきた。
As soon as the bell rang, the customers all came in at once.