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.
一、整句中时一般不放句末，句首后要有逗号，句中1、按一般副词使用2、做插入语（这两个分得清吧）
eg.1、Therefore，we must learn English well.
2、They therefore can learn English well.
3、Many fast food restaurant ,therefore,have red furniture or walls.
二、用在分句中，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。
eg.1、I had a headache;therefore I could not go to your party.
2、I was ill,and therefore could not come.
3、These birds are very beautiful and therefore liked by many people.
therefore的用法2：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。
therefore的用法3：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。
例句如下：
1. The truth is that junk bonds were misnamed, and therefore misunderstood.
事实上人们对垃圾债券的称谓有误，所以产生了误解。
2. They had seen him trawling and therefore knew that there were fish.
他们曾见过他用拖网，因此知道那里有鱼。
3. Men are anxious to improve their circumstances, but are unwilling to improve themselves; they therefore remain bound.
我们总是渴望改善周遭环境，但是却不愿意改善自己，因此总停留在原地，无法进步。
4. He is only 17 and therefore not eligible to vote.
他只有17岁，因此没有投票选举的资格。
5. He lost his health, and therefore his difficulties increased.
他身体虚弱, 因此更增加了他的困难.本回答被网友采纳
都表示“因此”，therefore 和 thereby 用法和含义不尽相同。