完成式
A .現在完成式：主詞(S)+have/has+過去分詞
1 )表動作或情境發生或未發生在「此刻」之前的某個不確定時間
例：Tim has already eaten lunch .
2 )表動作在「此刻」之前的某個不確定時間曾發生過數次
例：I have eaten at the restaurant twice .
B .SINCE和FOR的差別
1 )SINCE：主詞(S)+have/has+過去分詞+since+特定的時間點
例：I have been here since 1999 .
2 )FOR：主詞(S)+have/has+過去分詞+for+一段時間
例：I have been here for two hours .
C .現在完成進行式：主詞(S)+have/has+been+V-ing
1 )表動作始於過去持續到現在
例：She has been sitting in class since nine o’clock .
She has been sitting in class for thirty minutes .
| Already已經 | I have already finished my homework . |
| Yet 尚未 | I have not eaten lunch yet . |
| Still 仍然 | She still works at the bookstore . |
| Anymore 不再 | He does not live in this town anymore . |
D.過去完成式：主詞(S)+had+過去分詞
1 )表活動在過去的某特定時間點之前就已經完成(比過去還過去)
例：I had eaten dinner when Bob came .
E .未來完成式：主詞(S)+will have+過去分詞
1 )表在未來某個時間就會已經完成的事
例：They will have been married for 20 years by next January .