句子的主要動詞為過去式時，一般從屬子句的動詞也要用過去式。 下列都是表示時間的從屬連接詞： after, before, when, while, as, by the time (that), since, until, as soon as, once, as/so long as, whenever, every time (that), the first time (that), the last time (that), the next time (that)。