# Thread: Must VS Have to

1. Senior Member
Join Date
Apr 2004
Posts
1,148

## Must VS Have to

Dear teachers,

- What is the difference between HAVE TO and MUST?

- Could HAVE TO express a greater certainty from the speaker than MUST?

1) a) There HAS (got) TO BE a mistake.

b) There MUST BE a mistake.

2a) My friend MUST BE ill = Present; strong deduction: I am sure he is ill?
b) My friend HAS TO BE ill = Present; It’s more certain than with must ?

c) My friend HAD TO BE ill = Past; expresses a certainty?
d) My friend MUST HAVE BEEN ill. = Past: expresses a certain deduction ?

e) My friend OUGHT TO BE ill. (correct ? ) = Present : strong assumption ?
f) My friend SHOULD BE ill. (incorrect ?) = Present : weaker expectation / assumption
than “ought to” ?

- What’s the difference between deduction / expectation / assumption ?

Hela

2. ## Re: Must VS Have to

Originally Posted by hela
Dear teachers,

- What is the difference between HAVE TO and MUST?

- Could HAVE TO express a greater certainty from the speaker than MUST?

1) a) There HAS (got) TO BE a mistake.

b) There MUST BE a mistake.

2a) My friend MUST BE ill = Present; strong deduction: I am sure he is ill?
b) My friend HAS TO BE ill = Present; It’s more certain than with must ?

c) My friend HAD TO BE ill = Past; expresses a certainty?
d) My friend MUST HAVE BEEN ill. = Past: expresses a certain deduction ?

e) My friend OUGHT TO BE ill. (correct ? ) = Present : strong assumption ?
f) My friend SHOULD BE ill. (incorrect ?) = Present : weaker expectation / assumption
than “ought to” ?

- What’s the difference between deduction / expectation / assumption ?

Hela

Must to is used when you have the obligation coming from yourself, and have to when there is something external that obliges you to do something.

I must stop smoking once for all.

I have to abide by the rules of this forum.

One important difference to take into account is that "must not/ mustn't" does not mean that you don't have an obligation but that you are forbidden to do something (prohibition)

You must not smoke in here. It is forbidden.

I have not to do that homework today. I can do it tomorrow.

Must: It is used mostly to express the conclusion that something is certain. This is used in British English.

Have to: Used in American English

You must be Anna's sister -you look just like her.

You have to be joking! (AmE) / You must be joking! (BrE)

In the past tense you can only use MUST

I hear you've been to Patagonia. That must have been interesting. (NOT)
"that has to have been interesting"

Hope this helps! Maeve

3. Senior Member
Join Date
Apr 2004
Posts
1,148

## Re: Must VS Have to

Yes it does, thanks Maeve!

Hela

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•

Search Engine Optimization by vBSEO 3.6.1