I think so

I think so

An expression of vague affirmation or assent. A: "It's starting to get dark out, should we start heading home?" B: "I think so."
See also: think
Farlex Dictionary of Idioms.
See also:
  • think back
  • go against the flow
  • What are you on?
  • never in a month of Sundays
  • think out of the box
  • What color is the sun in your world?
  • never in a million years
  • what planet are you on?
  • What planet is (someone) on?
  • what planet is someone on?