when
/wɛn
/interrogative adverb
1At what time: when did you last see him? [with preposition]: since when have you been interested?...
- He said it was expected to be reopened to pedestrians today but it was not yet clear when it would open to traffic.
- This is as well as not knowing when they will arrive.
- We don't know when the pub will reopen, although we hope it will be as soon as possible.
1.1How soon: when can I see you?...
- When can I see you?
1.2In what circumstances: when would such a rule be justifiable?...
- I was moving to Dublin and nobody was going to tell me when and where to smoke.
- When will we meet again?
relative adverb
At or on which (referring to a time or circumstance): Saturday is the day when I get my hair done...
- Cancun has shown once again that we are living in a time when great struggles are shaping history.
- We must not return to the days when former Home Secretaries cut police numbers.
- On a day when big stories leapt off the leaderboard, Donald was among the best.
conjunction
1At or during the time that: I loved maths when I was at school...
- Theatre is her first love and when she is not performing she can invariably be found among the audience.
- He was looking out the front door yesterday when I had it open to feed the hens.
- One survivor said a meeting was being held in an upstairs room when the blast occurred.
1.1After: call me when you’ve finished...
- There was silence in the room when she finished her description of her trip to Africa.
- Ideally, you start it when you arrive, and you finish sometime before you go on stage to show it.
- We are going to make her a book-nook in her room when we move and this cushion is a good start.
1.2At any time that; whenever: can you spare five minutes when it’s convenient?...
- She used to shout at the children when they left the room with it still on.
- If grown on a window ledge, it may be necessary to bring the plants into the room at night when there is frost.
- She can smoke as much as she wants when in her room and we get on just fine.
2After which; and just then (implying suddenness): he had just drifted off to sleep when the phone rang...
- He was about to dictate into his recorder about the progress of his work when his mobile phone rang.
- I had just nodded off to sleep when I was woken up by an almighty crash from their house.
- Devlin just followed her out into his bedroom, when his cell phone started ringing.
3In view of the fact that; considering that: why bother to paint it when you can photograph it with the same effect?...
- You cannot claim to give the facts straight when there is no-one giving the other view.
- I am in the fourth year of my own fight, which is considered a long time when you have the kind of cancer I have.
- It is fantastic to even consider him when he has not been a pupil for two years.
4Although; whereas: I’m saying it now when I should have told you long ago...
- People could at times be standing at the back when there was room in the front of the train.
- They behaved as if they were in their living room at home, when, clearly they weren't.
- The danger is trying to put your nose through when there is no room and it ends in an accident.
Origin
Old English hwanne, hwenne; of Germanic origin; related to German wenn 'if', wann 'when'.