have to, must

Have to is NOT an auxiliary verb (it uses the verb as a main verb). We include have to here for convenience.

Must is a modal auxiliary verb.

In this lesson we look at have to, must and must not, followed by a quiz to check your understanding.

have to for objective obligation

We often use have to to say that something is obligatory, for example:

• Children have to go to school.

Note that we can use the have to expression in all tenses, for example: he has to, he had to, he has had to, he will have to

Structure of have to

Have to is often grouped with modal auxiliary verbs for convenience, but in fact it is not a modal verb. It is not even an auxiliary verb. In the have to structure, “have” is a main verb.

The basic structure for have to is:

subject
+
auxiliary verb
+
have
+
to-infinitive

Look at these examples in the Present Simple tense:

subject
auxiliary verb
main verb

to-infinitive

+
She

has
to work.
 

–
I
do not
have
to see
the doctor.

?
Do
you
have
to go
to school?

Use of have to

In general, have to expresses impersonal obligation. The subject of have to is obliged or forced to act by a separate, external power (for example, the Law or school rules). Have to is objective. Look at these examples:

• In France, you have to drive on the right.
• In England, most schoolchildren have to wear a uniform.
• John has to wear a tie at work.

In each of the above cases, the obligation is not the subject’s opinion or idea. The obligation comes from outside.

We can use have to in all tenses, and also with modal auxiliaries. We conjugate it just like any other main verb. Here are some examples:

 
subject
auxiliary verb
main verb

to-infinitive
 

Past Simple
I
 
had
to work
yesterday.

Present Simple
I
 
have
to work
today.

Future Simple
I
will
have
to work
tomorrow.

Present Continuous
She
is
having
to wait.
 

Present Perfect
We
have
had
to change
the time.

modal may
They
may
have
to do
it again.

must for subjective obligation

We often use must to say that something is essential or necessary, for example:

• I must go.

Structure of must

Must is a modal auxiliary verb. It is followed by a main verb.

The basic structure for must is:

subject
+
auxiliary verb
must
+
main verb
base

The main verb is always the same form: base

Look at these examples:

subject
auxiliary verb

main verb
base

I
must
go
home.

You
must
visit
us.

We
must
stop
now.

must cannot be followed by to. So, we say:

• I must go now.
  I must to go now.

Like all auxiliary verbs,cannot be followed by. So, we say:

Use of must

In general, must expresses personal obligation. Must expresses what the speaker thinks is necessary. Must is subjective. Look at these examples:

• I must stop smoking.
• You must visit us soon.
• He must work harder.

In each of the above cases, the “obligation” is the opinion or idea of the person speaking. In fact, it is not a real obligation. It is not imposed from outside.

It is sometimes possible to use must for real obligation, for example a rule or a law. But generally we use have to for this.

We can use must to talk about the present or the future. Look at these examples:

• I must go now. (present)
• I must call my mother tomorrow. (future)

We cannot use must to talk about the past. We use have to to talk about the past.

must not for prohibition

We use must not to say that something is not permitted or allowed, for example:

• Passengers must not talk to the driver.

Structure of must not

Must is an auxiliary verb. It is followed by a main verb.

The basic structure for must not is:

subject
+
must not
+
main verb

The main verb is the base verb.

We often contract must not to mustn’t.

Look at these examples:

subject
auxiliary
must + not
main verb

I
mustn’t
forget
my keys.

You
mustn’t
disturb
him.

Students
must not
be
late.

NB: like all auxiliary verbs, must CANNOT be followed by to. So, we say:

• You mustn’t arrive late.
  You mustn’t to arrive late.

Use of must not

Must not expresses prohibition – something that is not permitted, not allowed. The prohibition can be subjective (the speaker’s opinion) or objective (a real law or rule). Look at these examples:

• I mustn’t eat so much sugar. (subjective)
• You mustn’t watch so much television. (subjective)
• Students must not leave bicycles here. (objective)
• Policemen must not drink on duty. (objective)

We can use must not to talk about the present or the future:

• Visitors must not smoke. (present)
• I mustn’t forget Tara’s birthday. (future)

We cannot use must not to talk about the past. We use other structures to talk about the past, for example:

• We were not allowed to enter.
• I couldn’t park outside the shop.

WATCH:

Do You Know When To Use Whose?

What do who’s and whose mean?

 is the possessive form of the pronoun , while  is a contraction of the words  or .

However, many people still find  and  particularly confusing because, in English, an apostrophe followed by an  usually indicates the possessive form of a word. (For example, a purse belonging to a woman is “the woman’s purse.”) Not the case here, though. So, to help clarify further, watch this video that illustrates the differences and read more below!

When do you use who’s?

The first thing to figure out when deciding between who’s vs. whose is whether you need one word (whose) or two (who’s). Substitute the words who is, (and then who has) into your sentence. If either substitution works: who’s is your word. is a contraction of who is or who has. A contraction is a shortened form of two or more words where the omitted letter (or letters) is replaced by an apostrophe. So, when the bears in Goldilocks and the Three Bears ask each other “Who’s been sitting in my chair?”, it can also be understood as “who has been sitting in my chair?” And, if you’re wondering “Who’s going to write these words with more confidence?”, we hope that the answer to who is patting themselves on the back right about now is you.

Example sentences using who’s

 

• Who’s as strong as an ox?
• My aunt is someone who’s living in California.
• Tony told me who’s coming to the party.

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When do you use whose?

The word  is possessive, and it is often used as an adjective, which is a word that describes or clarifies a noun or a pronoun. So, in this case, whose is a possessive adjective, because it describes who owns something. Traditionally,  was only used to describe a person or several persons, as in “Sarah, whose dog is cute, just arrived.” In this case,  indicates which person’s (Sarah’s) dog we’re talking about. Imagine it’s raining and you grab an umbrella, only to realize later that it isn’t yours. You might ask your friend “Whose umbrella is this?” In other words, you’re asking who owns the umbrella.

Over time, it’s become grammatically acceptable to use to describe things belonging to inanimate objects and places, as well. “New York is a city whose lights burn brightly all night long.” Here, the lights belong to the city.

Example sentences using whose

 

• Whose dog chewed up my homework?
• You and whose army!?
• The ring came from a fire whose light was as bright as a star.
• When I figure out whose paper this is, I’ll sign it.

What about its vs. it’s?

And, since you might already be thinking it . . . yes, the same confusion also exists between the homophones  and . , with no apostrophe, is the possessive form of the pronoun (it’s never its’), while  is a contraction of the words  or .