therefore的用法以及与because、for的区别

　　therefore有两种用法,一在整句中,一在分句中.therefore是副词,但有时具有连词作用.

　　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、They therefore can learn English well.

　　2、Therefore,we must 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 was ill,and therefore could not come.

　　2、I had a headache;therefore I could not go to your party.

　　3、These birds are very beautiful and therefore liked by many people.

　　注：therefore是副词，但有时具有连词作用

　　therefore，otherwise 和 thus 的区别

　　Therefore要加逗号，后面跟句子(注意是句子);

　　Thus不一定要加逗号，后面不一定跟句子。

　　I was helping my sister with her study.Therefore,I failed to pass the exam.

　　Air carry the virus to everywhere,thus causing the explosion of the disease.(无逗号，thus 后面不是句子)

　　Air carry the virus to everywhere.Thus,it causes the explosion of the disease.(逗号，thus 后面是句子)

　　用于句型“祈使句+or+陈述句”中，表示在以祈使句为条件下的相反假设，意为“否则，要不然”。

　　例如： Work hard,or you will fall behind.你要努力学习，否则会落后。