一、for

可表示“因為”，但引導的不是從句，而是分句，對前面情況加以解釋，常用逗號把它和前面的分句分開，這在書面語中比較多見（口語中多用because, as, since等）：

1、The days were short, for it was now December.

白天很短，因為現(xiàn)在已經(jīng)是十二月。

2、He took the food eagerly, for he had eaten nothing since dawn.

他吃得很香，因為白天亮起他就沒吃東西。

3、The children soon lost their way, for they had never been in the forest before.

孩子們很快迷了路，因為他們從未進過這座森林。

二、so

表示結(jié)果，可譯為“因此”、“所以”：

1、Nobody seemed about, so I went in.

附近似乎沒人，因此我走了進去。

2、The play began at eight, so they must dine at seven.

我八點開始，所以他們得七點吃飯。

3、She felt very tired so she went to bed early.

她感到很疲倦，于是早早就睡覺了。

三、therefore

副詞，也表示同樣的意思，但比較文氣一點，可以放在分句前：

1、There is fog at Heathrow; therefore the plane has been diverted.

希斯羅機場有霧，因此飛機改到別的機場降落。

2、It rained; therefore the game was called off.

天下雨了，比賽因此取消。

四、hence

也是副詞，也表示類似意思，多用在說理性文章中，且多用在分句或句子開頭：

1、My mother is by herself; hence I must go home now.

我媽一個人在家，因此我得回去了。

2、Microwaves have got cheaper and hence more people can afford it.

微波爐便宜些了，因此更多的人買得起了。

3、Hence he was annoyed by many unwelcome attentions.

因此許多不受歡迎的殷勤舉動惹得他不高興。