动词根据构成谓语方式可分成两种:1构成合成谓语的特殊动词.共有12个.2.可以单独构成谓语的普通实义动词.
be动词有双重属性,当be是特殊助动词时,可以和doing/done/to do/going to do/used to doing/构成合成谓语.
He is leaving.
The work is finished.
The president is to visit your country next week.
I am going to have a trip in a few days.
当be本身是实义动词时解释为是,在等含义时,就不能再和其他实义动词连用了.通常要把那个动词变成to do或doing来做表语了.
To see is to believe.
Seeing is believing.