Question

for , since 表因为时在句子的区别。

Answer 1

for+时间段,since+时间点， since 表示从什么时候开始
例子 since 2004
是指 2004到现在
for
是指一段时间
例子 for 2004 to 2006
指的是04年到06年
SINCE后面加时间点
例如 SINCE 1990 意思就是从1990开始
1990就是一个时间点；
而FOR后面是加时间段
例如 FOR 5 YEARS
意思就是5年的时间
since+过去某一时间或句子,for+一段时间
She has taught in the school for ten years. 她在这所学校教书已经10年了.
I haven't eaten anything since breakfast. 我从早饭起就一直没有吃东西.

Answer 2

since 意为"既然"，表示对方已知的无需加以说明的原因或事实，语气比because弱，但是比as 强。

例如：Since we have no money, we can't buy that vase.

既然我们没钱，我们就不能买那花瓶。

Since everybody is here, let's begin our party.

既然大家都到了，那就开始我们的聚会吧！

for 是并列连词，用来附带解释说明前一分句的原因或理由，for引导的并列句，一般放在所要说明的句子的后面。

例如：I went to see him, for I had something to tell him.

我去见他，因为我有事要告诉他。

Answer 3

because:因为.强调直接原因.
since:因为.强调双方已知无需用说明的事由.
for:因为.强调一种推测.但不一定是事实.
as:强调一般因果关系.用于句首.
Because she's ill,she can't go to my home.因为她病了,所以她没有来我家.
注:because后接句子,而because of后接短语.
Since everyboby is here,let's begin our meeting.
既然大家都到了,那就开始开会吧.
Day breaks,fro the birds are singing.
因为鸟儿在唱歌了,天可能亮了.
As he was not well,i decided to go without him.
由于他身体不太好,我决定不带他去.

Answer 4

for,since是完成时的标志词，用于现在完成时，for+时间段，如:for two years,for third hours,for a month, since+时间点，如:since two years ago,since last Sunday,since two days