比较常见的有 after, before, since, till, until 等。如：

After lunch it began to rain. 午饭后开始下雨了。(after 为介词)

After you finish the letter show it to me．信写完后给我看看。(after 为连词)

You must come home before dark. 你必须在天黑前回家。(before 为介词)

I always bathe before I go to bed. 我睡觉前总要洗个澡。(before 为连词)

I have been here since last week. 我从上周起一直在这里。(since 为介词)

She has had another baby since I saw her last. 从上次我见到她以来，她又生了一个孩子。(since 为连词)