when S1 W1 /wen/ BrE AmE adverb , conjunction , pronoun
[ Language: Old English ; Origin: hwanne , hwenne ]
1 . at what time:
When are we leaving?
When did you first meet Dr Darnall?
When will the work be finished?
I don’t know when I’ll see her again.
when to do something
I’ll tell you when to stop.
2 . at or during the time that something happens:
Leonard was nine when his father died.
When the family came here from Russia, they were penniless.
When he was in the air force he flew Tornado jets.
3 . after or as soon as something happens:
When the meal was finished, Rachel washed up and made coffee.
I’ll phone you again when I get home.
4 . used to mention a type of event or situation when talking about what happens on occasions of that type:
When lead is added to petrol, it improves the car’s performance.
When mixed with water the powder forms a smooth paste.
He always wears glasses except when playing football.
5 . used to show which particular time or occasion you are talking about:
The best moment was when he scored the winning goal.
There are times when I hate him.
the day/time/afternoon etc when
She remembered the day when Paula had first arrived.
6 . by/since when before or since which time:
The baby is due in May, by when the new house should be finished.
That was written in 1946, since when the education system has undergone great changes.
7 . since when ...? spoken used to show that you are very surprised or angry:
Since when have you been interested in my feelings?
8 . even though something is true:
Why does she steal things when she could easily afford to buy them?
9 . used to introduce a fact or statement that makes something seem surprising:
When you consider that the airline handled 80 million passengers last year, the accident figures are really very small.
• • •
THESAURUS
▪ when at or during the time that something happens:
Call me when you get home.
|
When I got here, the place was empty.
▪ while during the time that something is happening – used to emphasize that something is continuing:
I’ll make the salad while you set the table.
|
While we were on holiday, our house was burgled.
▪ whenever used in order to emphasize that something always happens when another thing happens:
He visits his mother whenever he can.
|
You can come and talk to me whenever you have a problem.
▪ by the time used in order to say that one thing has or will have already happened when something else happens:
By the time a child is five, he will have watched hundreds of hours of television.
• • •
GRAMMAR
Generally, in a clause beginning with when that refers to the future, use the present tense or present perfect, not 'will':
▪
They don’t know what is going to happen when the project is finished (NOT when the project will be finished).
▪
Remove the supports when the glue has set.
However, when asking or talking about the time that something will happen, use will :
▪
When will the government take action?
▪
teenagers who don’t let their parents know when they will be home