连词:after, as, before, once, since, till, (not) until, as soon as, when, whenever (no matter when), while, as long as, no sooner.. than.., hardly/scarcely/barely. when.等
Tom had scarcely/hardly seen me when/before he left the room. 汤姆一看到我,就离开了房间。
名词短语:the moment, the minute, the instant, the second, every time 等
Each time he came to Shanghai, he would call on me. 他每次来上海,总是来看我。