1) for 因为，做并列连词使用时，是在对先行的句子补述原因或者理由，只可以连接句 子与句子，通常不置于句首。
He is absent today,for he is ill.
2) so,therefore 因此
He hurt his leg,so he couldn't play in the game.
I think,therefore I am.
3) then 那么，因而
Hide behind the wall, then they won't see you.
注意：
a.两个并列连词不能连用，但therefore,then,yet.可以和并列连词连用。
You can watch TV,and or you can go to bed.
He hurt his leg,and so / and therefore he couldn't play in the game.
b.although...yet，但although不与 but连用。
(错) Although he was weak,but he tried his best to do the work.(对) Although he was weak,yet he tried his best to do the work.
