when

when — adverb

1. used to ask about the time or occasion when something happens, or to refer to a

1.adverbA1
Definition

used to ask about the time or occasion when something happens, or to refer to a time that has already been mentioned.

Example

When did you last see your sister and her two young children?

direct question with did

Nala could not remember when the summer camp registration deadline was.

reported question after a verb of thinking

Common collocations
  • when + did/do/does
  • when + will/would
  • day when
  • time when
  • moment when
Synonyms
  • at what time

    more specific; asks for a clock time rather than a general occasion

  • on what day

    narrows the question to day of the week or date

Grammar Patterns

when + auxiliary + subject + verb

when + did/do/does + subject + verb

when + be + subject

noun + when + subject + verb

Usage Note

In direct questions, the verb follows the auxiliary (When did she leave?), not the subject (When she left?). In relative clauses, 'when' can often be replaced by 'that' or omitted in informal speech: 'the day (that) I met her'.

Common Mistakes

When you will arrive?
When will you arrive?
In direct questions the subject goes after the auxiliary verb, not before it.
Tell me when will you come.
Tell me when you will come.
In reported questions, the subject comes before the verb, not after it.

when — pronoun

when — conjunction

when — noun

Synonym discussion

Sense: adverb/1

All four words ask about time, but each targets a different dimension. 'When' is the broadest question word — it asks for any kind of time reference, from a century ('When did the Roman Empire fall?') to a second ('When did the doorbell ring?'). 'What time' narrows the question to a specific clock reading ('What time does the bank open?') and expects an answer like '9:30 a.m.' 'How long' asks about duration — the stretch of time from start to finish ('How long does the film last?'). 'How often' asks about frequency — how many times something happens within a period ('How often do you visit your grandparents?'). A learner who says 'What time do you visit your grandparents?' when meaning frequency would confuse a native speaker. To choose correctly, decide whether you need a point in time (when / what time), a duration (how long), or a repeated pattern (how often).

when ↗what timehow longhow often

Common collocations

Nouns

  • day when
  • time when
  • moment when
  • point when
  • year when

Adverbs

  • exactly when
  • just when
  • precisely when
  • right when

Phrases

  • when and where
  • when and how
  • since when
  • the when and the where

Prepositions

Etymology

Proto-Indo-EuropeanProto-GermanicOld EnglishMiddle EnglishEnglish

'When' comes from the Old English word 'hwanne' or 'hwenne', which was used both to ask questions about time and to link clauses about time. It belongs to a family of question words (who, what, where, why, how) that all trace back to an ancient Indo-European root *kwo-, used for asking questions. Over time, the spelling and pronunciation shifted from the Old English 'hw-' sound to the modern 'wh-' form we use today.