Usage of must, should, have to

[B]

i suppose HAVE TO is more similar to SHOULD as they both give the impression of "choosing what is morally right". there is a "sense of obligation" in both but not as much as with "MUST".

how can i clearly explain the difference among the three or at least between the two:MUST & SHOULD..?

i would appreciate any help you could give.

thanks very much.

[Jamie (K)]

"Must" and "have to" mean exactly the same thing, but "must" sounds more official and stronger.

"Have to" is not similar to "should". With "should" a choice is involved. With "have to" there is no choice, but only an obligation.

You'll notice that there is no past or future tense for "must", so when you put an auxiliary verb before it, it changes into "have to".

(Now): "He must make sure his assignments are done."
(Future): "He will have to make sure his assignments are done."

[B]

THANK YOU VERY MUCH FOR YOUR CLARIFICATION AND EXPLANATION, JAMIE K!!!