■ interrogative adverb
1》 at what time.
↘how soon.
2》 in what circumstances.
■ related adverb at which time or in which situation.
■ conjunction
1》 at or during the time that.
↘at any time that; ~ever.
2》 after which; and just then.
3》 in view of the fact that; considering that.
4》 although; whereas.
Origin
OE hwanne , hwenne ; of Gmc origin.