Um, let's see.... "I think" and "I believe" are basically the same for expressing your opinion about something. I personally use "I suppose" and "I guess" to imply that I don't agree with a statement, but I want to end the conversation. "I assume" and "I figure" is used to state you know something, but you don't have any actual proof that what you're saying is true. Hope I helped a little! <:

I think : You state your opinion. You are less in doubt and want to tell the other person what you think. This might/might not be a very strong belief. But it is strong nevertheless. I believe : A stronger version of I think. Here you are stating what you firmly think is true. Though it is still your own opinion but you are pretty sure that it is right. I suppose, I Guess : Implies some doubt or lack of conviction. You have a feeling that it is correct but you are not very sure I assume : Something that you assume or think may be true. There might be other options too but you assume this one. I figure : to conclude, judge, reason, or think about: I figured that you wanted me to stay.