because, since, as与for的用法区别

①  because表示原因语气最强，经常表示听者未知的原因，其引导的从句往往放于句末，成为信息的焦点。它既可以用来回答why的提问，又可以在强调句型中成为被强调的部分。

②  as语气较弱，较口语化，所表示的原因比较明显，或是已知的事实，故不需要强调。

③  since的语气也较弱，常表对方已知的事实，往往相当于汉语的“既然”。

for是并列连词，引导并列分句，用来表示附加说明，for引导的并列分句一般不放于句首。

Eg. He didn’t hear the knock on the door because he was listening to the radio.

   As it was a public holiday m all the shops were shut.

   Since we have no classes tomorrow, let’s go to the Great Wall

   Since the plan has been made, let’s get down to carrying it out

   I believe in her- for surely she would not lie to me

It’s going to rain , for my joints are aching