when
when
A1
adverb
/wen/
​
1 (used in questions) at what time; on what occasion
When did you last see him?
When can I see you?
When (= in what circumstances) would such a solution be possible?
2 used after an expression of time to mean ‘at which’ or ‘on which’
Sunday is the only day when I can relax.
There are times when I wonder why I do this job.
3 at which time; on which occasion
The last time I went to Scotland was in May, when the weather was beautiful.
when
conjunction
/wen/
1 at or during the time that
I loved history when I was at school.
2 after
Call me when you've finished.
3 at any time that; whenever
Can you spare five minutes when it's convenient?
4 just after which
He had just drifted off to sleep when the phone rang.
​ 5 considering that
How can they expect to learn anything when they never listen?
​6 although
She claimed to be 18, when I know she's only 16.
Idioms
as and when
if and when
pronoun
/wen/
​what/which time
Until when can you stay?
‘I've got a new job.’ ‘Since when?’
Word Origin
Old English hwanne, hwenne; of Germanic origin; related to German wenn ‘if’, wann ‘when’.