Modal Verb Meaning Expressing Example
I must stop when the traffic
to have to 100 % obligation
lights turn red.
must
logical conclusion He must be very tired after
to be very probable
(deduction) such enormous work
You must not smoke in the
must not not to be allowed to prohibition
hospital.
to be able to ability I can swim
can to be allowed to permission Can I use your phone please?
it is possible possibility Smoking can cause cancer !
When I was younger I could
to be able to ability in the past stay up all night and not get
tired..
could
Excuse me, could I just say
to be allowed to more polite permission
something?
it is possible possibility It could rain tomorrow!
to be allowed to permission May I use your phone please?
may
it is possible, probable possibility, probability It may rain tomorrow!
to be allowed to more polite permission Might I use your phone please?
might
I might come and visit you in
weak possibility,
it is possible, probable America next year, if I can save
probability
enough money.
need necessary necessity Need I say more?
lack of
I need not buy any tomatoes.
need not not necessary necessity/absence of
There are plenty in the fridge.
obligation
used to say or ask what
I should / ought to see a doctor.
is the correct or best 50 % obligation
I have a terrible headache.
thing to do
should/ought to suggest an action or
You should / ought to revise
to to show that it is advice
your lessons
necessary
logical conclusion He should / ought to be very
to be very probable
(deduction) tired after such enormous work
to suggest an action or
You 'd better revise your
had better to show that it is advice
lessons
necessary
Can and could
I can speak English means "I am able to speak English" or "I know how to speak English".
You can smoke here means "you may (are permitted to) smoke here" (in formal English may or might is
sometimes considered more correct than can or could in these senses).
There can be strong rivalry between siblings means that such rivalry is possible
Both can and could can be used to make requests: Can/could you pass me the cheese? means "Please pass me
the cheese" (where could indicates greater politeness).
May and might
The mouse may be dead means that it is possible that the mouse is dead.
You may leave the room means that the listener is permitted to leave the room.
May can indicate presently given permission for present or future actions: You may go now. Might used in this
way is milder: You might go now if you feel like it. Similarly May I use your phone? is a request for permission
(might would be more hesitant or polite).
Shall and should
Main article: Shall and will
The verb shall is used in some (particularly formal) varieties of English in place of will, indicating futurity,
when the subject is first person (I shall, we shall).
Shall is sometimes used in questions (in the first, or possibly third, person) to ask for advice or confirmation of
a suggestion: Shall I read now?; What shall we wear?
Should is sometimes used as a first-person equivalent for would (in its conditional and "future-in-the-past"
uses), in the same way that shall can replace will. Should is also used to form a replacement for the present
subjunctive in some varieties of English,
Will and would
The modal will is often used to express futurity (The next meeting will be held on Thursday). Since this is an
expression of time rather than modality, constructions with will (or sometimes shall; see above and at shall and
will) are often referred to as the future tense of English, and forms like will do, will be doing, will have done
and will have been doing are often called the simple future, future progressive (or future continuous), future
perfect, and future perfect progressive (continuous). With first-person subjects (I, we), in varieties where shall
is used for simple expression of futurity, the use of will indicates particular willingness or determination.
Must and had to
The modal must expresses obligation or necessity: You must use this form; We must try to escape. It can also
express a confident assumption (the epistemic rather than deontic use), such as in It must be here somewhere.
An alternative to must is the expression had to (in the present tense sometimes have got to), which is often more
idiomatic in informal English when referring to obligation. This also provides other forms in which must is
defective (see Replacements for defective forms above) and enables simple negation (see below).
When used with the perfect infinitive (i.e. with have and the past participle), must expresses only assumption:
Sue must have left means that the speaker confidently assumes that Sue has left. To express obligation or
necessity in the past, had to or some other synonym must be used.
The formal negation of must is must not (contracted to mustn't). However the negation effectively applies to the
main verb, not the modality: You must not do this means that you are required not to do it, not just that you are
not required to do it. To express the lack of requirement or obligation, the negative of have to or need (see
below) can be used: You don't have to do it; You needn't do it.
The above negative forms are not usually used in the sense of confident assumption; here it is common to use
can't to express confidence that something is not the case (as in It can't be here or, with the perfect, Sue can't
have left).
Mustn't can nonetheless be used as a simple negative of must in tag questions and other questions expressing
doubt: We must do it, mustn't we? Mustn't he be in the operating room by this stage?
Ought to and had better
Ought is used with meanings similar to those of should expressing expectation or requirement. The principal
grammatical difference is that ought is used with the to-infinitive rather than the bare infinitive, hence we
should go is equivalent to we ought to go. Because of this difference of syntax, ought is sometimes excluded
from the class of modal verbs, or is classed as a semimodal.
The reduced pronunciation of ought to (see Contractions and reduced pronunciation above) is sometimes given
the eye dialect spelling oughta.
Ought can be used with perfect infinitives in the same way as should (but again with the insertion of to): you
ought to have done that earlier.
The negated form is ought not or oughtn't, equivalent in meaning to shouldn't (but again used with to).
The expression had better has similar meaning to should and ought when expressing recommended or
expedient behavior: I had better get down to work (it can also be used to give instructions with the implication
of a threat: you had better give me the money or else). The had of this expression is similar to a modal: it
governs the bare infinitive, it is defective in that it is not replaceable by any other form of the verb have, and it
behaves syntactically as an auxiliary verb. For this reason the expression had better, considered as a kind of
compound verb, is sometimes classed along with the modals or as a semimodal.
The had of had better can be contracted to 'd, or in some informal usage (especially American) can be omitted.
The expression can be used with a perfect infinitive: you'd better have finished that report by tomorrow. There
is a negative form hadn't better, used mainly in questions: Hadn't we better start now? It is more common for
the infinitive to be negated by means of not after better: You'd better not do that (meaning that you are strongly
advised not to do that).
