因為，所以，雖然，但是

我們寫中文時，可以用「因為．．．．所以．．．．」這樣的句子結構。但請注意，英文則沒有這樣的結構；你可以只用「因為」，或只用「所以」，但不能同時用它們。

譬如你可以說： 

Because the weather is fine, we go for a walk. 

也可以說：

The weather is fine, so we go for a walk. 

但萬萬不能說： 

Because the weather is fine, so we go for a walk.  (wrong!)
Because the weather is fine, therefore we go for a walk.  (wrong!)

除了「因為．．．．所以．．．．」這個結構，「雖然．．．．但是．．．．」也有相同的規則。寫英文時，我們不可以用 "Although/though/even though...., but...." 這樣的結構： 

Although he exercises a lot, he's still very fat.  (okay)

He exercises a lot, but he's still very fat.  (okay)

Although he exercises a lot, but he's still very fat.  (wrong!)