so用作連詞，主要用於表結果，意為“所以”：

It’s very cold, so wear a heavy coat. 外邊很冷，因此穿一件厚大衣。

The door was locked, so we couldn’t get in. 門上鎖了，所以我們進不去。

I couldn’t have won, so I didn’t go in for the race. 我不可能獲勝，因此我沒參賽。

The play began at eight, so they must dine at seven. 戲八點開始，因此他們必須七點吃飯。

It was dark, so I couldn’t see what was happening. 天很黑，所以我看不見發生了什麼事。

There happened to be a policeman on the corner, so I asked him the way. 恰好拐角處有一位警察，我就向他問路了。

二、有時可與並列連詞and連用，構成習語and so(相當so)：

He told me to do it and so I did it. 他叫我那麼做，所以我就做了。

He worked hard and so he succeeded. 他勤奮工作，所以他取得了成功。

There was so much to eat and so few people to eat it. 有這麼多東西可吃，而吃的人又這麼少。

I forgot to post the letter, and so she never heard about my divorce. 我忘了寄那封信了，所以她一直不知道我離婚的事。

so用作並列連詞時主要表示結果，意為“因此”“所以”。如：I was tired, so I went to bed earlier. 我累了所以早點睡了。

按英語習慣，表示結果的so不能與表示原因的because套用，在使用時只能保留其中的一個。

誤：Because that was a difficult question, so I answered it last.

正：That was a difficult question, so I answered it last.

正：Because that was a difficult question, I answered it last.