I suppose (so)
An expression of vague affirmation or assent. A: "It's starting to get dark out, should we start heading home?" B: "I suppose so." Bob: "You look a little down today. Everything alright?" Mary: "I suppose. I've just been feeling vaguely melancholy lately."
I suppose so
I reluctantly agree, I guess so, as in Do you want tickets to the concert?-I suppose so, or Do you think it's going to rain?-I suppose so. [Mid-1500s]
I supˈpose so
used for showing that you agree but you are not happy about it: ‘Can I borrow the car?’ ‘Yes, I suppose so, but be careful.’‘Can I invite him to the party?’ ‘I suppose so.’