by經常是與完成時聯絡在一起，具體什麼完成時取決於by之後的時間，例如by 2013是過去完成時，by now是現在完成時，by 2015是將來完成時by＋時間”與動作性強的動詞連用時，主句多用於完成式。by 後的時間可指現在、 過去或將來時間點。如： By the time he was fourteen years old, he had learned maths all by himself. 到14歲的時候，他就已經自學了數學[SB 2B p.2]。I shall have finished it by the time you come back.你回來以前我就把它做完了[1]。By the end of the match, they had kicked two goals and we had kicked four. [JB p91] 比賽結束時，他們踢進了2分我們踢了4分。They must have finished their work by this time.他們現在一定已經完成工作了[2]。 但是，上述情況中當時間為將來時，主句動作發生在從句動作之後時，主句動詞可用一般時態。如：If you"re not better by then, I"ll take you to see the doctor. [JB3 p.85] 如果到那時還不好些，我就帶你去看病。Can you finish this by tomorrow? 在明天以前你能做完這件事嗎[1]？ 間或有用進行式的。如：By the end of the first week the head of the department was saying very nice things about me. 第一週末時系主任給我多多美言了幾句 [3]。
by經常是與完成時聯絡在一起，具體什麼完成時取決於by之後的時間，例如by 2013是過去完成時，by now是現在完成時，by 2015是將來完成時by＋時間”與動作性強的動詞連用時，主句多用於完成式。by 後的時間可指現在、 過去或將來時間點。如： By the time he was fourteen years old, he had learned maths all by himself. 到14歲的時候，他就已經自學了數學[SB 2B p.2]。I shall have finished it by the time you come back.你回來以前我就把它做完了[1]。By the end of the match, they had kicked two goals and we had kicked four. [JB p91] 比賽結束時，他們踢進了2分我們踢了4分。They must have finished their work by this time.他們現在一定已經完成工作了[2]。 但是，上述情況中當時間為將來時，主句動作發生在從句動作之後時，主句動詞可用一般時態。如：If you"re not better by then, I"ll take you to see the doctor. [JB3 p.85] 如果到那時還不好些，我就帶你去看病。Can you finish this by tomorrow? 在明天以前你能做完這件事嗎[1]？ 間或有用進行式的。如：By the end of the first week the head of the department was saying very nice things about me. 第一週末時系主任給我多多美言了幾句 [3]。