Past Perfect

過去完成式的句型為 "had" + 過去分詞。它用來表示某項動作是在過去另一項動作之前完成的。第一個事件 (had left for New York) 用過去完成式。第二個事件 (arrived at the airport) 則用簡單過去式。

如果句中有 "before" 或 "after" ，通常就不需要使用過去完成式，因為時間的關係十分明顯。所以可以改用簡單過去式，像第二句一樣。兩個句子的意義相同。

在這些句子中，過去完成式用來表達未實現的願望。在第一個句子中，說話者希望訂期相會，但是未能如願。在第二句中，說話者未能接獲 Mike 將會晚到的通知，但是希望之前若是能接到就好了。

I had hoped to make an appointment with him before he left.
I wish you had told me Mike was going to be late.

否定句的句型為將 "not" 置於助動詞 "had" 之後。

問句的句型為將助動詞 "had" 置於主詞之前。

THE PAST PERFECT TENSE Use the past perfect to show that an action was completed before another action in the past. Use the past perfect to describe the first action and use the simple past to describe the second action. Positive Statement S + had + past participle She had already left for New York when I arrived at the airport. Negative Statement S + had + not + past participle He hadn't called me in a few days, so I called him. Question Had + S + past participle? Had you met him before this evening? She had already left for New York when I arrived at the airport. (First she left for New York, and then I arrived at the airport.) In sentences with before or after, the past perfect is optional because the time relationships are already clear. Mike had left for London before I arrived at his house. Mike left for London before I arrived at his house. The past perfect can also be used to express an unrealized hope or wish. I had hoped to make an appointment with him before he left. I wish you had told me Mike was going to be late.

補充: https://www.youtube.com/watch?v=7sXGfQ6R6nc