Understanding and Using Modal Verbs: Understanding and Using Modal Verbs (#35)

The English modal verbs are often challenging for learners
of English. This happens for many reasons, including both
grammar and meaning.

In this Hint, we'll look at more about must.

One use for must (negative must not or mustn't) is in showing
a requirement.

Another use is in making conclusions--making guesses which
are based on strong, convincing evidence. These guesses may 
be either affirmative ( + ) or negative ( - ).

Examples:

Akihiro got a very high score on the TOEFL.
He must know English well.

(I conclude that Akihiro knows English well
because I know that the TOEFL is very difficult
and I also know that Akihiro got a very high score.)

I'm not sure what time it is, but judging by the sun,
it must be around 2:00 PM.

(I conclude that the time is around 2:00 PM because
I know the approximate times for different positions
of the sun.)

There are no lights and no one is answering the doorbell.
They must not be at home.

(Because there are no lights and because no one is
answering the doorbell, I conclude that no one is at home.)

When I said, "Could you help me?," that woman had
a blank look and said something in another language.
She must not know English.

(I conclude that the woman doesn't know English
because she had a blank look and because she said
something in another language.)

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Special Notes: