after幾種用法：
一、after作介詞的用法：
1.after+名詞，作為介賓短語，
如：after 5 o'clock。五點以后。
He ran after the bus.他在那輛公交車后追著跑。
2.after+動名詞，也是作為介賓短語，
如：after having finished my homework。完成我的作業后。
I will go to bed after drinking the milk.
3.after+代詞，作為賓語的主語，
如：He went home after he finished all the work
二、after做副詞的用法：
如：three hours after三小時后; He told me after that he had not enjoyed the film.他告訴我后來他一點都不想看電影。
三、after做連詞的用法：
如：I saw them after I arrived.我到了之后才看到他們。
用作連詞引導時間狀語從句時注意：若主句用將來時態(或含有將來意味)，則時間狀語從句要用一般現在時態 (表將來意義)表將來意義，而不能直接使用將來時態：他回來后我就走。正：I’ll leave after he comes back.誤：I’ll leave after he will come back.
after前后時態
1、遵循“主將從現”原則。
如：He will go to Beijing to work after he graduates from the university.
他大學畢業后將去北京工作。
2、從句表示的動作發生在主句動作之前，如果強調從句的動作發生在前，從句謂語要用過去完成時，主句用一般過去時。
如：He went out for a walk after he had finished the work.
他完成這項工作后他出去散步。
3、從句表示的動作發生在主句動作之前，如不強調動作的先后，主句和從句均用一般過去時。
如：He went to bed after he finished his homework last night.
昨晚他完成作業后上床睡覺。