区别辨析as、because、for与since

as、because、for与since这些连词均含有“因为”之意。

as :从属连词,语意较because, since弱,着重在主句,所表示的原因或理由是“附带的”。

  • As you were out, I left a message.
    你不在,所以我留了一张字条儿。
  • She may need some help as she's new.
    她是新来的,可能需要一些帮助。

because :从属连词,语意强,着重直接的原因或理由,所引出的从句是全句的重心,用以回答why提出的问题。

  • I did it because he told me to.
    是他吩咐我才做的。
  • Just because I don't complain, people think I'm satisfied.
    就因为我不发牢骚,大家便以为我满意了。

for :并列连词,语气较弱,所引出的句子一般放在后面,表示附带说明的理由或推断理由。

  • The town is famous for its cathedral.
    这个城镇以大教堂著名。
  • She gave me a watch for my birthday.
    她送给我一块手表作为生日礼物。

since :语意比because弱,但比as强,一般用于表示“由于大家已知的事实”。

  • 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。