when

Universal Words adverb, pronoun, conjunction adverb 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. pronoun what/which time: Until when can you stay? * 'I've got a new job.' 'Since when?' conjunction 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 see ASconj.