I have to do something =it is necessary to do it,I am obliged to do it
We use do/does/did in question and negative sentences
What do I have to do to get a new driving license?
not What have I to do
Karen doesn’t have to work Saturdays.
not Karen hasn’t to
Must is similar to have to
- It’s later than I thought.I must go. or I have to go.
You can use must or have to when you give your own opinions
(for example, to say what you think is necessary, or to recommend someone to do something)
Mark is a really nice person.You must meet him./You have to meet him.
We use have to(not usually must) to say what someone is obliged to do.This is a fact,not the speaker’s own opinion.
I have to work from 8.30 to 5.30 every day .
But we use must in written rules and instructions:
- Applications for the job must be received by 18 May
We use had to(not must) to talk about the past:
- I went to the meeting yesterday, but I had to leave early.
Mustn’t and don’t have to are completely different
You mustn’t do something=don’t do it
You must keep this a secret. You mustn’t tell anyone
You don’t have to do something=you don’t need to do it(but you can if you want)
You don’t have to come with me .I can go alone.
You can use have got to instead of have to
- I’v got to work tomorrow. or I have to work tomorrow.
- When has Helen got to go? or When does Helen have to go?