—used to say that something is required or necessary
You have to follow the rules.I told him what he had to do.We have to correct these problems soon or the project will fail.I have to remember to stop at the store."Do you have to go?" "Yes, I'm afraid I really have to."I didn't want to do it but I had to.
—also have got to
You've got to stop.
Note: There is a difference in meaning between not have to, "it is not necessary to," and must not, "is not allowed to."
2
—used to say that something is required by a rule or law
All passengers have to exit at the next stop.All passengers have got to exit at the next stop.
3
—used to say that something is desired or should be done
You have to read this book. It's fantastic!You have to come visit us soon.You really have to see the doctor about that cough.You have got to come visit us soon.
4
—used to say that something is very likely
It has to be close to noon.She has to be the most beautiful woman I've ever seen.He has to have a lot of money to live the way he does.There has to be some mistake.There has got to be some mistake.
5
—used in various spoken phrases to emphasize a statement
I have to say, I was surprised to hear from him.She's a talented actress, you have to admit.I have to admit, I expected better results.It has to be said that the movie was not very good.I have to warn you, this will not be easy.I have got to say, I was surprised to hear from him.
6
—used in questions or statements that express annoyance or anger
Do you have to be so unreasonable?Why does it always have to rain on the weekend?It has got to rain on the day when we planned a picnic.