1課 時間関係 教科書 p.8〜11
Time relation — just now… then, as soon as, since
接続：動辞書形 ＋ や／や否（いな）や
Just… immediately…. Almost synonymous with 〜が早いか, but written, more formal.
注意 / Note：Only used for events that have already happened. The latter does not use will/command. Often describes an immediate chain reaction.
比較 / Compare：〜や否や ≒ 〜が早いか but more formal, written; often seen in the news.
よく出る形 / Common form：動辞書形＋や／や否や。Only used for things that happened.
そのニュースが伝わるや否や、株価は急落した。
As soon as the news spread, the stock price immediately plummeted.
赤ちゃんは母親の顔を見るや、泣きやんだ。
As soon as the baby saw his mother's face, he immediately stopped crying.
ドアが開くや否や、乗客が一斉に降り始めた。
As soon as the door opened, passengers all stepped out.