Expression
Usually written in kana
1.  when it comes to ...;  if one were to speak of ...;  when one hears ...
Conjunction
Expression
Usually written in kana
2.  by ... you mean ...;  when you say ... you mean that ...;  so that means
sometimes in sentence-initial position
Expression
Usually written in kana
3.  whenever ...;  if it's ... then (without fail)
indicates that what follows is inevitable