"I think I won't be late."
Is this sentence grammatically correct? Is it possible to say it in place of, "I don't think I'll be late."
Hello, Bananas, and welcome to the Grammar Exchange!
Yes, the sentence "I think I won't be late" is grammatically correct, and it is possible to use it instead of "I don't think I'll be late."
But since "I don't think I'll be late" is the usual expression, putting "not" in the other clause would generally be done in special circumstances, for emphasis:
A: I won't be late.
B: Are you sure? He thinks you will.
A: Well, I think he's wrong. I think I won't be late.