〜や否や／〜や

Meaning

Indicates that as soon as one thing happens, the next follows almost simultaneously. 「〜や」 is stiffer and more literary. A written-style expression for the swiftness of successive actions.

Examples

彼は知らせを聞くや否や、現場へ駆けつけた。 As soon as he heard the news, he rushed to the scene.
その商品は店頭に並ぶや否や、瞬く間に売り切れた。 The product sold out in no time as soon as it appeared on the shelves.
彼は席に着くや、堰を切ったように話し始めた。 The moment he sat down, he began talking as if a dam had burst.