The Word is:”when”
1. at what time.
“when can I see you?”
“when would such a rule be justifiable?”
1. at or on which (referring to a time or circumstance).
1.at or during the time that.
“call me when you’ve finished”
“can you spare five minutes when it’s convenient?”
2. after which; and just then (implying suddenness).
3. in view of the fact that; considering that.
4. although; whereas.
Source credit: Google