when

1 when /ˈwɛn/ adverb
1 when
/ˈwɛn/
adverb
Britannica Dictionary definition of WHEN
1 
: at what time
2 
a  : at, in, or during which
b  : at or during which time
3 
informal : at a former and usually less successful time
2 when /ˈwɛn/ conjunction
2 when
/ˈwɛn/
conjunction
Britannica Dictionary definition of WHEN
1 
a  : at or during the time that
b  : just after the time that
c  : at any or every time that
2 
a  — used to say what happens, is true, or can be done in a particular situation
b  — used to ask why or how something is done in the situation that exists
3 
: in spite of the fact that : although
4 
: the time or occasion at or in which
3 when /ˈwɛn/ pronoun
3 when
/ˈwɛn/
pronoun
Britannica Dictionary definition of WHEN
: what or which time

since when?

— see 1since