ملخص الدرس / الثآنية ثانوي/اللغة الإنجليزية/Grammar/Must - have to -had to- Must be

Modals of obligation and necessity

Must:

Forms:

possitive  Negative  Interrogative 
I/you/he/she/we/they must go now I/you/he/she/we/they must not/ musn't go now

must I/he go now

when must I/you... go?  

 

Meaning:

Must= obligation 

we use must when we think it is important or essential to do an action .

In England ,you must drive on the left, but in Algeria, you must drive on the right .

Musn't= negative of obligation prohibition .

we use musn't when we think that it is important or essential not to do an action .

we musn't drive fast here.the road sing says that the speed limitis 50 kms per hour

have to

positive  Negative  Interrogative 
Zohra is a nurse.some times she has to work on weekends Yasmine is a teacher she does not have /doesn't have to/needn't work on weekend. 

Does Yasmine have to work on weekends?

yes, she does.

Meaning:

have to : obligation 

in positive sentences, we often use have to express obligation .in this case, have to is little different form must. 

In Algeria, you have to be 18 before you're allowed to take your driving licence test .

have to : necessity:

We can use have to to talk about an action that is neccessary.

We have to eat in order to live.Eating is neccessity because there is no other possibility for staying alive .

compare: 

you dont have to/needn't do this exercise .it's optional .Absence /lack  of obligation .

you mustn't cheat in the exam.it's forbidden. Prohibition/ negative obligation .  

Meaning:

have to : obligation 

in positive sentences, we often use have to express obligation .in this case, have to is little different form must. 

In Algeria, you have to be 18 before you're allowed to take your driving licence test .

have to : necessity:

We can use have to to talk about an action that is neccessary.

We have to eat in order to live.Eating is neccessity because there is no other possibility for staying alive .

compare: 

you dont have to/needn't do this exercise .it's optional .Absence /lack  of obligation .

you mustn't cheat in the exam.it's forbidden. Prohibition/ negative obligation .