used for referring back to a possibility, fact, or situation that has just been mentioned
I think/suppose/expect/hope etc so: You’re in love with Rita, aren’t you? I thought so.
‘You’re not really going to resign?’ ‘No, I don’t suppose so.’
say so/tell someone so: If you wanted to leave early, you should have said so.
so they say/so they tell me/so I understand: I’m a quick learner. Or so they tell me.
if so: Does the President intend to go to Moscow? And if so, when?
more so/less so/very much so: ‘Is Sybil the outdoor type?’ ‘Oh yes, very much so.’