Have to

Have to (/ˈhæf tu:/) is an English semi-modal verb. It is one of the most frequent structures used to express obligation, especially when coming from “outside,” imposed by an authority, reality, etc. It uses the verb have with a to-infinitive as the main verb.

Meaning

Normally, we use have to to express a future event that we see as an obligation now. If we refer to a more distant future, we can use will have to, as in We’ll have to do it sooner or later.

The negative is “don’t have to" - which expresses lack of obligation, i.e. if "you don’t have to do something,” you can do so if you want to, but are not obliged. Note this is different from mustn’t, which expresses prohibition.

Have to is very similar in meaning to need to, and at low levels the difference is probably best ignored.

Have got to is very often used interchangeably with have to but actually expresses more immediate obligation: I have to do it sometime today. vs I’ve got to do it right now. We do not use “got" in the past tense or "pure" future, (I had to do it - I’ll have to do it later.), except when using the present tense as a future (I have to do it later.).

Form

This conjugates with third person -s in the present tense. The past tense form and past participle form is "had to.” The present participle form is "having to.”

Use of "have to" with have, e.g. “I have to have a meeting" or “I’ll have to have it fixed" is sometimes confusing for learners. Emphasising that this is acceptable and emphasising the difference between "have to,” "have" and “have something done.”

The grammar for have to is the same as the grammar for need to.

Pronunciation

Normally there is devoicing /'hæf tə, 'hæs tə / in spoken sentences: I have to go; He has to go.

“To" can be pronounced as /tu:/ or reduced to a schwa /tə/.

Appropriacy

Have to is slightly less formal than using must; however, it is more formal than the related have got to.

Pedagogy

Some EFL learners (especially Chinese it seems) have a tendency to overlook the devoicing in pronunciation and pronounce have to as */ˈhæv tu:/. Although this is likely to be understood, it is an extremely common structure and mispronunciation does contribute to foreign accent.