when

American  

[hwen, wen, hwuhn, wuhn] / ʰwɛn, wɛn, ʰwən, wən /

adverb

1. at what time or period? how long ago? how soon?.

   When are they to arrive?

   When did the Roman Empire exist?

2. under what circumstances? upon what occasion?.

   When is a letter of condolence in order?

   When did you ever see such a crowd?

---

conjunction

1. at what time.

   to know when to be silent.

2. at the time or in the event that.

   when we were young;

   when the noise stops.

3. at any time; whenever.

   He is impatient when he is kept waiting.

4. upon or after which; and then.

   We had just fallen asleep when the bell rang.

5. while on the contrary; considering that; whereas.

   Why are you here when you should be in school?

pronoun

1. what time.

   Till when is the store open?

2. which time.

   They left on Monday, since when we have heard nothing.

noun

1. the time of anything.

   the when and the where of an act.

when British  

/ wɛn /

adverb

1. 1. at what time? over what period?

      when is he due?

   2. ( used in indirect questions )

      ask him when he's due

2. to state when an action is to be stopped or begun, as when someone is pouring a drink

3. (subordinating) at a time at which; at the time at which; just as; after

   I found it easily when I started to look seriously

4. although

   he drives when he might walk

5. considering the fact that

   how did you pass the exam when you'd not worked for it?

6. at which (time); over which (period)

   an age when men were men

---

noun

1. (usually plural) a question as to the time of some occurrence

when Idioms  

More idioms and phrases containing when

• cross a bridge when one comes to it
• push comes to shove, when

---

Usage

When should not be used loosely as a substitute for in which after a noun which does not refer to a period of time: paralysis is a condition in which (not when ) parts of the body cannot be moved

Etymology

Origin of when

First recorded before 1000; Middle English when(ne), Old English hwenne; cognate with German wann “when,” wenn “if, when” (compare Gothic hwan “when, how”); akin to who, what

Example Sentences

Healey's resignation as defence secretary comes on the day so many in Westminster expected would be when the government's long anticipated Defence Investment Plan was published.

From BBC • Jun. 11, 2026

It lowered its full-year guidance when it reported first-quarter earnings last month after an expensive investment into a prediction-market platform.

From Barron's • Jun. 11, 2026

O'Neill knows a player when he sees one but in his second and then third coming at Celtic last season he never gave the impression of a man who is out there sourcing these guys.

From BBC • Jun. 11, 2026

For example, Samsara’s cameras used in delivery trucks can help determine when a driver is distracted or drowsy, and deliver real-time alerts.

From Barron's • Jun. 11, 2026

There is no way to tell when a Flash will appear or how long the Flash will be.

From "Split the Sky" by Marie Arnold