根据其在句中的功能,动词可分为行为动词、系动词、助动词和情态动词四类,有些动词是兼类词.如：
We have lunch at 12.我们12点吃午饭.(have是行为动词)
We have been to New York.我们去过纽约.(have是助动词)
W I am hungry.我饿了.(am是连系动词)
She was beaten on the way home.她在回家的路上被人打了.(was是助动词)
You needn’t have waited for me.你本来不必等我.(need是情态动词)
The door needs painting.这个门需要油漆了.(needs及物动词)