Modal verbs 1 (must and have to)

MUST & HAVE TO

MUST = HAVE TO

HAVE TO is used more often because MUST sounds too strict

MUST: it's very very important

HAVE TO: it's necessary

Negative: NEEDN'T (it's not necessary)

DON'T HAVE TO (nobody told me to do it)

Question: DO YOU HAVE TO?

Past: HAD TO / DIDN'T HAVE TO / DID YOU HAVE TO?

Future: WILL HAVE TO

COMMON PROBLEMS:

1) CAN'T – MUSTN'T – NEEDN'T – DON'T HAVE TO – SHOULDN'T

I can't do it. (I have no time, I don't know how)

I mustn't do it. (It's prohibited.)

I needn't do it. (It's not necessary. I can do it, but there is no need)

I don't have to do it. (Nobody told me to do it. It's my responsibility)

I shouldn't do it. (It's not a good idea)

2) DIDN'T HAVE TO (not HADN'T)

I had to get up early. X I didn't have to get up so early.

3) NEEDN'T and DIDN'T HAVE TO

NEEDN'T is only used in the present:

I needn't buy any bread.

BUT

I didn't have to buy any bread yesterday.

4) MUST and HAD TO

MUST is used only in the present:

I must study more.

BUT

I had to study hard last week.