therefore用法：
用作副詞(adv.)
therefore的意思是“因此,為此,所以”,是副詞,引導結果、結局或結論,不能誤作連詞用。
therefore可引出壹個獨立句,但不能連接兩個句子,因此當therefore前沒有and等連詞時,前面須用分號。
連接副詞therefore用於句首時後面無需逗號,若位於句中前面可加也可不加逗號。
therefore也可用於推理,作“故…,由此得出”解。
He was the only candidate; therefore, he was elected.
他是唯壹的候選人，因此，他當選了。
We do not have enough money. Therefore we can not afford to buy the new car.
我們的錢不夠,因此買不成這輛新車。
I was ill, and therefore I could not come.
我病了,所以沒能來。
He was very tired, and therefore he didn't give the market report.
他非常疲倦，所以沒能作市場報告。
：
therefore是副詞，但有時具有連詞作用。
1、當therefore在整句中時，它壹般不放句末，放在句首後要有逗號，放在句中時前後都要有逗號。
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、當therefore用在分句中時，即壹個句子壹部分表示原因壹部分表示結果。
這時壹般詞前要用分號，其後用不用逗號無所謂。若第二個分句前是逗號或無符號，則要註意therefore是副詞，和so不壹樣，要保持句子完整，應用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、在我們英語考試中，大家最好用therefore 別用so。因為so比較簡單，顯得文章水平低，而用therefore會顯得妳的作文更好，更容易引起閱卷人的註意，給閱卷人好的印象。
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.