conj (1)自从……以后(来)(from a certain time till now or till a later past event)(主句通常用现在完成时、过去完成时或一般现在时，从句用过去时或现在完成时)：He has been at home (ever)～he returned from America. 自从美国回来以后他就一直待在家里。I have been working (ever)～I finished my breakfast. 自从吃完早饭以后我就一直工作。He came at last. I had been waiting for him for an hour～you left. 他终于来了。自你们走后我又等了他一小时。It's a long time～we met last. 我们已经很长时间没有见面了。It was ages～I had my last meal，and I was very hungry. 上一顿饭已经吃过好长时间了，我饿极了。I've known her～I've lived in this street. 自从我住到这条街上，我就认识她了。

(2)因为，既然(because;as)：S～he was busy，he didn't come to the party. 他因为忙没有来参加那个聚会。Aircraft noise is a problem～we are close to the airport. 由于我们靠近机场，飞机噪音就成了一个问题。S～you're not interested，I won't tell you about it. 既然你不感兴趣，我就不告诉你那件事了。

prep 自从……以后(来)(from a certain time till now or till a later past time)[通常与现在完成时、过去完成时或一般现在时连用]：She has never spoken to him～then/last week. 从那时/上周以来她就没有和他说过话。 It's been raining～two o'clock. 从两点起天就一直在下雨。I met her last Christmas，but I had known her by sight～1995. 我是在去年圣诞节时认识她的，但是我从1995年起就和她见过面。It's a long time～the last meeting. 自从上次会议以来已经过了好长时间了。It was ages～my last meal，and I was very hungry. 上一顿饭已经吃过好长时间了，我饿极了。

adv 从那时起，后来(from then till now or a later past time)[与现在完成或过去完成时连用]：He left here five years ago and I haven't seen him (ever)～. 他五年前离开这里，从那时起我就再也没有见过他。I bought a new car two years ago but I've～sold it. 两年前我买了一辆新车，但是后来我又卖了。

【辨异】since与as、because和for的区别见AS。