what is the different between since and for

what is the different between since and for
what is the different between since and for

what is the different between since and for
1.表时间：since 自从.,接时间点,句子用完成时.如; They have been working on the project since the the end of last year.
for+时间段,表示一个动作持续了多长时间,也用完成时.如：I have
learned English for ten years.
2.表原因：since 从属连词,“既然”,如：Since everybody is here ,let's begin our lesson.
for 并列连词,引导的并列句要放在后面.如:he didn't go to school,for he was ill.

1.since（既然）语气较弱，强调已知的事实。
例：Since you can't answer the question, I'll ask someone else.
既然你回答不出这个问题，我就问别人了。
2.for（因为）的用法：
for是并列连词，表示推断的原因，或对前一分句补充说明理由。
例：It must be morning fo...

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1.since（既然）语气较弱，强调已知的事实。
例：Since you can't answer the question, I'll ask someone else.
既然你回答不出这个问题，我就问别人了。
2.for（因为）的用法：
for是并列连词，表示推断的原因，或对前一分句补充说明理由。
例：It must be morning for the birds are singing.一定是清晨了，因为鸟儿在叫。
3.because （因为）的用法：
because通常表示直接的原因。because引导的从句表示直接而明确的原因和理由，表示按因果关系的推断，语气很强，用来回答why的问题, 一般位于主句之后。
例：We couldn't go out because it was too cold. 因为天气太冷，我们不能外出。
4.now that（既然）的用法：
now that同since相似，语气较弱，强调人们已知的事实。例：
Now that you are busy, let me do it for you.
既然你忙，就让我给你做吧。
区别：since和now that，表示事物发展的自然结果，特别是当对方大概已经了解其原因的情况下使用，表示既成事实的原因一般位于主句之前。注意：for是并列连词，引出的原因较间接，似乎是事后所想到的补充解释的理由，只陈述一般推断的理由，不一定表示产生结果的必然原因，主要放在两个并列句之间。because通常表示直接的原因。

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当两个都当作是"因为"的意思时意义也不同
eg.
jump for joy
the west lake is noted for its scenery
for 作因为解时表示的是一个直接的原因
he didinot came,since he was busy
since this method doesnot work,let us try ab...

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当两个都当作是"因为"的意思时意义也不同
eg.
jump for joy
the west lake is noted for its scenery
for 作因为解时表示的是一个直接的原因
he didinot came,since he was busy
since this method doesnot work,let us try abother.
since做原因状语从句的引导词,一般表示客观原因.

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since + 过去的时间，或+过去式的句子。( 点时间）
for + 段时间
eg : He has lived here since 1987./ 2 years ago.
They have taught English since they came here.
He has waited for you for an hour.
两个句子的动词应该用的是延续性动词。

since可用在句首，而for不能

since 后跟的是一个具体的时间点
for 后一般跟的是一段时间
它们都用于完成时态