for与since区别：含义不同、词性不同、用法不同。for可作介词和连词，含义有关于、因为、由于，表示对象、用途等；since可作介词、连词和副词，含义有自…以后、既然、此后、后来。
一、for的中文含义及用法介绍
1、作为介词时，意为(表示对象、用途等)给，对，供;以帮助;为了;关于。
例句：There's a letter for you.
有你一封信。
Can you translate this letter for me?
你能为我翻译这封信吗？
They are anxious for her safety.
他们为她的安全担心。
I am speaking for everyone in this department.
我代表这个部门全体人员讲话。
2、作为连词时，意为因为;由于。
例句：We listened eagerly, for he brought news of our families.
我们急不可待地听着，因为他带来了我们家人的消息。
I believed her─for surely she would not lie to me.
我相信她的话——因为她肯定不会向我撒谎。
二、since的中文含义及用法介绍
1、作为介词时，意为自…以后;从…以来;(表示气愤)何曾，什么时候。
例句：She's been off work since Tuesday.
星期二以来她一直没上班。
Since when did he ever listen to me?
他什么时候听过我的话？
Since the party she had only spoken to him once.
那次聚会以后，她只和他说过一次话。
2、作为连词时，意为从…以后;自…以来;因为;由于;既然。
例句：Cath hasn't phoned since she went to Berlin.
卡思自从去了柏林还没有打来过电话。
We thought that, since we were in the area, we'd stop by and see them.
我们想，既然到了这个地方，就该顺便去看看他们。
3、作为副词时，意为自…以后;从…以来;此后;后来。
例句：He left home two weeks ago and we haven't heard from him since.
他两周前离家外出，我们至今还没有他的音信。
The original building has long since been demolished.
原来的建筑老早就拆了。
