OBLIGATION AND NECESSITY

When we want to say that someone has an obligation to do something, or that it is necessary for them to do it, you use “must” or “have to”

Example:

You must come to the meeting tomorrow.

I enjoy parties, unless I have to make a speech.

 

There is sometimes a difference between “must and “ have to”. When you are stating your own opinion that something is an obligation or necessity. You normally use “must”.

 

Example:

I must be very careful not to upset him.

We must eat before we go.

 

When you are giving information about what someone else considers to be an obligation or a necessity, you normally use “have to”.

 

Example:

They have to pay the bill by Thursday.

They have to pay the bill by Thursday.

She has to go now.

 

Note: you normally use “have to” for things that happened repeatedly, especially with adverbs of frequency such .

 

Example:

I always have to do the shopping.

You iften have to wait a long time for a buast.'

Must:

(+) Subject + must + verb 1 +c

(-) subject +must + not + verb 1 +c

(?) must +subject + verb 1 +c?

 note :

must not = mustn't

have to/ has to 

(+) Subject + have/has to+ verb +C

(-) Subject + do/does + not + verb + c

(?) do/does +Subject +verb + c?

note :

i, you, they, we + have / do not have to.....

she, it, he  + has/ doesn't have to.....