非谓语动词是指在句子中不是谓语的动词,主要包括不定式、动名词和分词（现在分词和过去分词）,即动词的非谓语形式.
不定式 I want to open/close the door.我想开/关门.
动名词 Would you mind opening/closing the door?你介意开/关一下门吗?
现在分词The flower is opening.花正在开放.
When is the bookstore closing?这家书店什么时候结束营业?
过去分词：Suddenly he heard the door opened.突然,他听到门关上了.
Why do you keep your eyes closed你干嘛把眼睛闭上?