think

judge or regard; look upon; judge

I think he is very smart

expect, believe, or suppose

I imagine she earned a lot of money with her new novel

use or exercise the mind or one's power of reason in order to make inferences, decisions, or arrive at a solution or judgments

I've been thinking all day and getting nowhere

recall knowledge from memory; have a recollection

I can't remember saying any such thing

imagine or visualize

Just think, you could be rich one day!