1. after兼有两种词性:介词和连词。
2. after做介词时,后面只能加名词/代词/动名词短语(doing sth),形成介宾短语,做句子的状语(时间状语/地点状语)。
如:After finishing my homework, I watched TV last night. 时间状语
She is running after me. 地点状语
3. after做连词时,引导一个时间状语从句,意思是“在...之后”。该从句是个完整的句子。
如:I watched TV after I finished my homework.
参考资料:原创回答团(159号会员)