Today, i will finish this revision with the subjects: [NO] OBLIGATION / PROHIBITION / ADVICE OR OPINION (with must, have to and should), DEDUCTION (with must, may, might, can´t) and ABILITY / POSSIBILITY.
[NO] OBLIGATION / PROHIBITION / ADVICE OR OPINION
– Must and have to a very similar meaning. Have to is more common for general, exernal obligations, for exemple rules and laws. Must is more common for specific (i.e. on one occasion) or personal obligations.
I have to wear a shirt and tie at work (it´s the rule in this company)
I must buy a new shirt (it´s my own decision)
– Have to is a normal verb and it exists in all tenses
– Must is a modal verb. The only forms are must and mustn´t.
– You can also use have to or must for strong recommendations.
NO OBLIGATION / NECESSITY
You don´t have to pay for the tickets. They´re free.
You don´t have to go to the party if you don´t want to.
– Don´t have to and mustn´t are completely different.
You musn´t drive along this street (It´s prohibited, agains the law).
You don´t have to drive (You can drive if you want to but it´s not necessary / obligatory)
– You can often use can´t or not allowed to instead of mustn´t
– Have got to is often used instead of have to in spoken english.
ADVICE OR OPINION
– Should is not as strong as must / have to. We use it to say if we think something is the right or wrong thing to do.
– Should is a modal verb. The only forms are should and shouldn´t.
– You can also use ought to and ought not to instead of should / shouldn´t.
You should take warm clothes with you to Dublin. It might be cold at night.
– We often use must, may / might, can´t to say how sure or certain we are about something.
– In this context, the opposite of must is can´t NOT mustn´t.
When you are sure something is true: MUST
They must be out. There aren´t any lights on.
When you think something is possibly true: MAY or MIGHT
She´s not at home. She may be working.
She might not like that skirt. It´s not her style.
When you are sure something is impossible / not true: CAN´T
He can´t be ill. I saw him at the gym.
ABILITY AND POSSIBILITY
This subject is too simple.
When the phase was in past tense, you MUST use COULD!¹
When the phase was in present tense, you MUST use CAN!
When the phase was in future tense, you MUST use BE ABLE TO!²
¹Also, you SHOULD use COULD in questions.
²Next to BE ABLE TO, you HAVE TO put the verb in a infinitive way.
A hug for everyone!