什么叫陈述语气、祈使语气、虚拟语气

陈述语气用来陈述事实或询问事情,用于陈述句,疑问句或感叹句中.
eg：The sun is larger than the earth.
Does Tom usually get up very early?
What a clever boy!
祈使语气表示劝告、命令、希望或禁止等,用原形动词开始,主语常被省略.eg:Give me some candies first.
虚拟语气用来表示说话人的主观愿望或假想,而不表示客观存在的事实,所说的是一个条件,不一定是事实,或与事实相反.
eg:If I were you,I would go at once.
其中每个下面都有很多分类.