同样是表示缘由的,为何for是并列连词,而because是从属连词?
它两个能互换么？
for 和 because 作为连词都可表示缘由。
because引导的分句为状语，所以可以坐落于主句前，也可以坐落于主句后。比如：
He feels very weak because he is ill.
Because he is ill, he feels very weak.
for作为并列连词，用来引出并列分句，讲解说话人为何会说前面的话。所以，for只能坐落于二个分句之间。比如：
They were certainly there,forI saw them.
不能说：For I saw them, they were certainly there.
并列连词and, but, so都可以坐落于句首，表示本句和前一句之间的逻辑联系。比如：
He sings well. And he dances well too.
He was ill. But he continued working.
He can keep it. Or he can give it to someone else.
for和其他并列连词一样，也可以如此用：
They were certainly there. For I saw them.
because则一般不能这么用，除非是口语中回答“why.
They were certainly there. Because I saw them.
because 可以替换 for, 但for未必能替换because。比如：
They were certainly there, for/because I saw them.
He sold his house, because he needed money for his sons operation.
for=I say so because...
