In a previous section, you learned how
should can be used to express advisability:
--The front desk clerk should give us
Another way should can be used is in expressions
--They have been working hard. They should
(In this example, should means will probably.)
The past form (should have) means that
the speaker expected something that did
--I haven't heard anything from them.
They should have called by now.
Could is used in two ways in English:
1.) Past ability:
--I can speak English now. I couldn't
when I was a child.
2.) Polite questions:
--Could I borrow your car?
--Could you speak slower?
--Could we check out later?
Note that could is the simple past form
of the verb can. The negative form of
it is couldn't (could not).
Must/Have To/Have Got To
Must and have to both express necessity:
--You must fill out this form.
--You have to pick up Mr. Roberts.
In some situations, must is more urgent
or stronger than have to:
--You must be here for your appointment
on time. I have a busy schedule today.
--You have to take another course next
The expression have got to is similar
in meaning to must and have to but is
reserved for spoken English:
--I have got to study more. (i.e., I must
Using May and Might
Two other important modal verbs are may
and might. The two are used interchangeably
in standard American English to express
probability or possibility:
--You may be wrong.
--You might be wrong.
--The attorney might be late.
--The attorney may be late.
The past form is expressed as follows:
modal (may/might) + have + past participle
--I may/might have left my glasses in
NOTE: Must can also be used to express
--The plane must be leaving now.