therefore用法：
用作副词(adv.)
therefore的意思是“因此,为此,所以”,是副词,引导结果、结局或结论,不能误作连词用。
therefore可引出一个独立句,但不能连接两个句子,因此当therefore前没有and等连词时,前面须用分号。
连接副词therefore用于句首时后面无需逗号,若位于句中前面可加也可不加逗号。
therefore也可用于推理,作“故…,由此得出”解。
He was the only candidate; therefore, he was elected.
他是唯一的候选人，因此，他当选了。
We do not have enough money. Therefore we can not afford to buy the new car.
我们的钱不够,因此买不成这辆新车。
I was ill, and therefore I could not come.
我病了,所以没能来。
He was very tired, and therefore he didn't give the market report.
他非常疲倦，所以没能作市场报告。
拓展资料：
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.