used in questions to ask at what time something happens
When is your birthday?
Do you know when the train leaves?
✦ Old English “hwænne”, from Proto-Germanic *hwan, meaning “at what time”.
at or during the time that something happens
Turn off the lights when you leave the room.
He was cooking when the phone rang.
✦ Developed from Old English subordinating use of “hwænne,” keeping the sense of “at the time that.”
the time or date at which something happens
We still have to decide the when of the ceremony.
Let’s talk about the where and the when.
✦ Noun use recorded from the 1700s, abstracted from the adverb to mean “the specific time.”
every time that something happens or at any time that something might happen
Whenever the baby cries, her father picks her up.
Take a break whenever you feel tired.
at whatever time; at an unspecified time, especially in questions or when no particular time is important
Call me whenever; I'm usually at home in the evenings.
We can start the meeting whenever suits you best.
(informal, US) at the specific time that; when (used for a single past event)
I was driving to work whenever I saw the accident.
He called me whenever he got home last night.
