what's the difference between, have to-must- should in english language?

Answer 1

should

Should is used to give advice and make recommendations and to talk about obligation, duty and what is expected to happen. Reference is to the present and the future. Should is similar to must but is not as strong as must:

You should always wear a helmet when you go out cycling on busy roads.


Once the pack is opened, the cooked meat inside should be consumed within three days.


Should I tell her that her son is playing truant and skipping school? ~ I think you should. She should know about it.



should and should have

Should combines with the perfect infinitive to form should have + past participle when we want to talk about past events that did not happen, but should have happened. We are talking about an expectation and referring back to past time. Compare the following:

Before Tom leaves for work, his wife advises him:

You should take your umbrella. It might rain. ~ No, I'll be all right. I shan't need it.

But it did rain. When he arrives back home, his wife says:


What did I tell you? You should have taken your umbrella. Then you wouldn't have got wet.

Reference to the present and future:


You should try and smoke less, Henry. Your health isn't very good and it's getting worse.

Reference to the past:


I should have given up smoking years ago, Mary. If I had, I wouldn't be in such bad shape now.



would

If we want to talk about an unreal or unlikely situation that might arise now or in the future, we use a past tense in the if-clause and would + infinitive in the main clause. Compare the following and note that would is often abbreviated to 'd:

How would you manage, if I wasn't here to help you? ~ I'd manage somehow. I wouldn't bother to cook. I'd go out to eat or bring home a take-away. I'd ask your mother to help me with the washing and the ironing. I know she'd help me.
would have

If we want to refer to the past and make a statement about things that did not happen, we need to use had + past participle in the if clause and would have constructions in the main clause. Note in these sentences that we can use 'd as the abbreviation for both had in the if-clause and would in the main clause:

If he'd taken an umbrella, he wouldn't have got wet on the way home.


If he'd taken his umbrella, he'd have stayed dry.


could

Could can be used to ask for permission, to make a request and express ability in the past. Compare the following:

Could I borrow your black dress for the formal dinner tomorrow? ~ Of course you can!


Could you do me a favour and pick Pete up from the station? ~ Of course I will!


I could already swim by the time I was three. ~ Could you really? I couldn't swim until I was eight.
could have

As with would have, and should have, could have is used to talk about the past and refers to things that people could have done in the past, but didn't attempt to do or succeed in doing:

I could have gone to university, if I'd passed my exams.


If he'd trained harder, I'm sure he could have completed the swim.


Note the difference between would have and could have in the following two examples. Would have indicates certainty that he would have won if he had tried harder, could have indicates that it is a possibility. Might have is similar in meaning to could have, although the possibility is perhaps not quite as great:
If he'd tried a bit harder, he would have won the race.

If he'd tried a bit harder, he could have won the race.

If he'd tried a bit harder, he might have won the race.

Answer 2

Indian boy is a proper linguist. I am however a Canadian old guy and what was slang when I was young is proper English now. With the advent of this inturnut stuff, ur English is dfrnt agn. god bless us all.lol I have to do my home work because my mommy says that I must, But I refuse even though I know that I should. You should trust indiaboy on this one, not that you must, or that you have to. Have to is very slangy, and is what a kid says, Ooohhh, do I have to? or what old guys say, I really have to pay my taxes, really I have to!! does this in any way help?

Answer 3

"Have to" and "must" are used the same way, they mean that the person does not want to do something, but they are required to. I can guess that "must" implies that you have no choice, "you must do this" and "have to" is slightly less of an obligation, "you have to do this for me". "Should" means that you do not have to, nor must you do the thing, but you feel either morally, or because of social pressure, that you need to do something, like "you should do what your father would do". Hope that helps. I'm offering the uses that are used commonly in english, but the official definitions differ slightly.

Answer 4

"have to" and "must" mean about the same thing; whatever it is can't NOT be done. "have to" kind of implies someone else insisting (as in "Mom says I have to get off the phone")

"should" means there are excellent reasons for doing it, but it is still optional

Answer 5

YOU MUST BREATHE OR YOU WILL SUFFOCATE.
YOU SHOULD BELIEVE ME , BUT YOU DON'T HAVE TO .
MAKE ANY SENSE ?

Answer 6

doesnt make sense,do you mean have to MUCH