通俗一点的讲,两个动词遇到的时候需要用to连接.比如：go to swim,want to go,这种叫做非谓语动词,也叫动词不定式.如果不加to do的时候可以是do+doing,例如go swimming,like singing.还有一些词后面只能加动词ing形式.入：enjoy doing,keep doing