在英语学习中，表因果关系或对等关系的连接词有：therefore, so, as a result, as the result of …，because of, due to …,owing to, thanks to等。
therefore意思是结果、对某事进行推论、因此、所以、故、乃，therefore的用法在英语学习中也很广泛：它有两种用法：
therefore是副词，但有时具有连词作用。

1、当therefore在整句中时，它一般不放句末，放在句首后要有逗号，放在句中时前后都要有逗号。
例如：Therefore，we must learn English well.
They therefore can learn English well.
Many fast food restaurant ,therefore,have red furniture or walls.

2、当therefore用在分句中时，即一个句子一部分表示原因一部分表示结果。
这时一般词前要用分号，其后用不用逗号无所谓。若第二个分句前是逗号或无符号，则要注意therefore是副词，和so不一样，要保持句子完整，应用and therefore。
例如：I had a headache，therefore I could not go to your party.
The truth is that junk bonds were misnamed, and therefore misunderstood.
They had seen him trawling and therefore knew that there were fish.

3、在我们英语考试中，大家最好用therefore 别用so。因为so比较简单，显得文章水平低，而用therefore会显得你的作文更好，更容易引起阅卷人的注意，给阅卷人好的印象。
The lime water has turned cloudy, therefore carbon dioxide has been produced during the experiment.
Rescue workers are therefore drilling a hole on the north side of the mine.