(interrogative) At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time.

At (or as soon as) that time that; at the (or any and every) time that; if. / During the time that; at the time of the action of the following clause or participle phrase. / At what time; at which time.

(interrogative) What time; which time.

The time at which something happens.

(often humorous) That's enough: a command asking someone to stop adding something, especially an ingredient or portion of food or drink; used in, or as if in, literal response to 'Say when'.

Contraction of when is. / (informal) Contraction of when has. / (informal) Contraction of when does. / (colloquial) Contraction of when was.

(law, finance, business) Used to indicate the timing and contingency of some obligation in contracts, especially financial.

(informal, chiefly law) In the event that the thing being discussed comes to pass.

(philosophy) Existence at a particular point in time.

plural of when