1. 若since引导的状语从句的谓语是终止性动词的过去时，则从句表示的时间是“从动作开始的那—时刻起”。例如：He has studied very hard since he came to our school.自从他来到我们学校，他学习就非常努力。

2. 若since引导的状语从句的谓语动词是持续性动词或表示状态动词的过去时时，则从句表示的时间是“从动作或状态结束时算起”。例如：I haven’t heard any noise since I slept. Sleep为持续性动词，sleep的动作结束时，即“醒来”时，所以这句应译为“我醒后还未听到任何声音”。

3. 若since引导的状语从句的谓语为持续性动词的现在完成时，则表示动作和状态延续到现在(说话时刻)，其表示的时间的起点应从动作发生之时算起。例如：I haven’t heard from him since he has lived there. 这里has lived表示动作的持续性，时间的起点应从:“开始居住”时算起。因此此句可理解为“自从他(开始）住在那儿起，我就一直没收到他的来信”。

双语例句：

1. Since your daughter is one of my regular patients, I'm stretching a point.由于你的女儿常来我这里看病，我就破一次例。

2. I don't think he has any friends since he grassed to the Feds.由于他向联邦调查局特工告过密，所以我想他已没有任何朋友。

3. The economy is mired in its longest recession since the second world war.经济陷入二战以来最长衰退期。

4. The imposition of surcharges was something the federation had opposed since its outset.额外收费是联合会从一开始就反对的东西。

5. The crimp on take-home pay has been even tighter since taxes were raised.自从税收提高后，对实得工资的限制更严了。

6. She touched her locket for luck, a superstition she had had since childhood.她摸了摸项链上的小盒子以求明迹神吉利，这是她从小形成的一种迷信想法。

7. She has been on the board since its inception two years ago.自从两年前开业起她就是董事会的成员了。

8. [as adv.] she ran away on Friday and we haven't seen her since.她星期五逃走了，自那以后我们再也没有看见她。

9. She had logged more than 12,000 miles since she had been launched.自船只下水以来航程已达12000余英里。

10. The paper has lost millions of readers since its heyday in 1964.这份报纸自1964年它的鼎盛时期以来读者少了几百万。