by the time
by the time — idiom
1. used to say that a situation or action has already been completed before or at t
used to say that a situation or action has already been completed before or at the moment when another event happens, often emphasizing that the first event is finished before the second begins.
By the time the firefighters arrived, the barn had already collapsed.
past perfect in main clause for completed past event
By the time the concert ended, the last train had already left the station.
By the time you finish this course, you will have learned over five hundred words.
By the time Dr. Okafor read the test results, she had already suspected the problem.
- before
stronger emphasis on one event happening earlier than another; 'by the time' adds the nuance of completion up to a deadline or reference point
- when
can sometimes substitute in informal use, but 'when' does not carry the meaning of completion before a reference point
- by
a shorter equivalent used before a specific time or age ('by age 30' = 'by the time he was 30'), but cannot be used before a full clause
文法句型
by the time + [clause], [main clause with perfect tense]
用法筆記
The time clause after 'by the time' uses a simple tense (past for past reference, present for future reference). The main clause typically uses a perfect tense — past perfect for completed past events and future perfect for future events. Example: 'By the time she arrives, I will have cooked dinner.' (NOT 'I will cook dinner.')