加过去分词，构成完成时态。已经;曾经have/has done现在完成时 had done过去完成时will have done将来完成时would have done过去将来完成时have/has been doing现在完成进行 had been doing过去完成进行。
have sb do 使某人做某事=make sb do sth
have sbdoing 使某人持续做某事=keep sb doing
have sth done 使某事被做=make sth done
e.g.：They haven't finished the job yet.他们尚未完成该项工作。(用于虚拟语气，表示与过去事实相反的假设)(假如那时)……的话
She might have come if she hadn't been so busy.当时若不是那么忙，她是可能来的。
The teacher have us read new words every morning.老师让我们每天读新单词。
In order to keep warm, we have the fire burning all the night.为了取暖，我们让篝火一直燃烧着。
My computer doesn't work now, and I will have it repaired later.我的电脑坏了，等会我会让它被修理的。（让别人修理）
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