when
when — adverb
1. used to ask about the time or occasion when something happens, or to refer to a
used to ask about the time or occasion when something happens, or to refer to a time that has already been mentioned.
When did you last see your sister and her two young children?
direct question with did
Nala could not remember when the summer camp registration deadline was.
reported question after a verb of thinking
Autumn is the season when the leaves on the maple trees turn bright red.
When should I call the repair shop to check on my laptop?
I still remember the day when my grandfather taught me how to fish.
- at what time
more specific; asks for a clock time rather than a general occasion
- on what day
narrows the question to day of the week or date
文法句型
when + auxiliary + subject + verb
when + did/do/does + subject + verb
when + be + subject
noun + when + subject + verb
用法筆記
In direct questions, the verb follows the auxiliary (When did she leave?), not the subject (When she left?). In relative clauses, 'when' can often be replaced by 'that' or omitted in informal speech: 'the day (that) I met her'.
常見錯誤
when — pronoun
1. used after a preposition to ask about a point in time or to refer to a time that
used after a preposition to ask about a point in time or to refer to a time that has already been mentioned.
Since when have you been taking guitar lessons every weekend?
since when — asks about the starting point
Until when is the library open on Friday evenings?
until when — asks about the end point
From when does the new bus schedule begin operating?
Since when did Asher become so interested in learning Japanese history?
- what time
can replace 'when' after prepositions in many contexts: 'From what time...?'
文法句型
preposition + when
用法筆記
This pronoun use is almost always restricted to questions and follows a small set of prepositions (since, until, till, from, by). It cannot stand as a direct object or subject of a verb (*I know when, as a pronoun meaning 'what time' is not standard in this position — that use belongs to the adverb sense).
常見錯誤
when — conjunction
1. used to introduce a fact that makes something else in the same sentence seem sur
used to introduce a fact that makes something else in the same sentence seem surprising, unreasonable, or self-contradictory.
How can you say you are too tired to help when you stayed up playing games until midnight?
when + clause introducing a contradictory fact
Why would anyone trust that report when the writer has admitted it contains many errors?
It seems unfair to criticise the volunteers when none of the critics have offered to help themselves.
It is strange that Dr. Park recommended rest when she told us to exercise every day.
- given that
more formal; states a precondition rather than a contradiction
- seeing that
slightly informal; common in British English
文法句型
question + when + clause
statement + when + clause
用法筆記
This sense nearly always appears in a rhetorical question or a statement expressing surprise, criticism, or contradiction. It is different from the temporal 'when' (adverb sense), which simply marks a point in time.
常見錯誤
❌ 'When you finish, please call me.' (temporal, not contradictory) — This is the adverb sense of 'when', not the 'given that' conjunction use. Compare: 'How can you leave when the work is not done?' (contradictory use).
2. used to say that something is true or happens even though another fact would nor
used to say that something is true or happens even though another fact would normally prevent it or make it seem unexpected.
Rin decided to take the job when the salary was much lower than her previous position.
concessive when — the salary was lower, yet she still took the job
The Watanabe family bought a new car when their old one was still running perfectly well.
Noor insisted on paying for dinner when the restaurant had offered to give us free meals.
Élise continued to use her old phone when the screen had been cracked for over a year.
- although
more common; the standard concessive conjunction
- even though
stronger contrast; more emphatic than 'when'
文法句型
clause + when + clause
用法筆記
Distinguish this concessive sense from conjunction/1 (GIVEN THAT): here the main clause states an action or fact that happens regardless of the 'when' clause, rather than a contradiction being pointed out. This sense is rarer and mostly found in formal writing.
常見錯誤
❌ 'I was sleeping when the phone rang.' (temporal, not concessive) — This is simply marking simultaneous time. For the concessive 'when', you should be able to replace it with 'although': 'I took the job when (= although) the pay was low.'
when — noun
1. the point in time when something happens or is arranged to happen, especially in
the point in time when something happens or is arranged to happen, especially in the fixed phrase 'the when and where'.
Please tell me the when and where of the wedding ceremony so I can book my flight.
fixed phrase: the when and where
The police are trying to determine the when of the accident from witness statements.
We have agreed on the budget; now we need to settle the when of the project launch.
The when and how of the payment should be written clearly in the contract.
文法句型
the when [of something]
the when and where
用法筆記
The noun sense is almost always used in the paired expression 'the when and where' or paired with other question words ('the when and how', 'the when and why'). It is rarely used alone as a standalone noun.