forget to do　忘记要去做某事。　(未做)

　　forget doing　忘记做过某事。(已做)

　　The light in the office is stil on. He forgot to turn it off.

　　办公室的灯还在亮着，它忘记关了。(没有做关灯的动作)

　　He forgot turning the light off.

　　他忘记他已经关了灯了。　 ( 已做过关灯的动作)

　　Don't forget to come tomorrow.

　　别忘了明天来。 (to come动作未做)

　　典型例题