have to
fixed phrase.fixed phrase. you use this to say that something is necessary or that you are forced to do it.
fixed phrase. a semi-modal auxiliary used to express objective obligation or necessity. Unlike 'must', it is frequently used for obligations imposed by external rules or circumstances.
I have to go to work now.
In this country, you have to drive on the left side of the road.
The committee members have to reach a unanimous decision before the fiscal year concludes to secure the necessary funding.
the 'to' is followed by the base form of a verb.
contrast with 'must' for internal vs. external obligation; 'have to' is much more common in spoken English and can be used in all tenses.
I must to go.I have to go.learners often confuse 'must' and 'have to', incorrectly adding 'to' after 'must'.