MODAL VERBS

Modal verbs are: must, can, could, may, might, will[1], would, should, ought to.

There are also full (lexical)[2], and primary verbs which can be used with modal meaning. These are need, have and dare.

 

MORPHOLOGY

Modal verbs do not add –s in the third person singular.

Questions are formed by putting the modal before the subject (Can I have another glass of wine, please?)

 Negatives are formed by putting not after the modal

(You can't/cannot be serious)

They are followed by a bare infinitive (without to)

 

USE/MEANING

Must

Must only has one form. It is not used in the past, doesn't have a continuous or perfect form. Must expresses (a strong) necessity. We use it to say that something is necessary now or in the near future. (I must tidy up my wardrobe. I can't find a thing there anymore).

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Have to is also used in this sense, but there is AN IMPORTANT DIFFERENCE ESPECIALLY IN BRITISH ENGLISH!!!!!!!!!!!

 

We use must when the speaker decides what is necessary and have to when the necessity comes from the situation (I have to buy a ticket to get on the next train-THAT'S THE RULE)

(You must wear a frilly dress to the homecoming -I'm telling you)

Also, must is used to express a strong recommendation (You MUST check out the latest episode of The Big Bang theory! It's a blast!)

 

To express something we see as a logical certainty

(You say you just saw a green cow? You must be drunk or something)

But, to express certainty in questions and negatives, can is used instead of must (Who can it be?)

 

Although it is not used for past necessity, must when combined with the perfect form of the verb is used to make conclusions about the past (We went to Rome last month. That must have been nice)

 

When must is used in the negative it means prohibition (Americans also use can't in this sense) (You mustn't talk during class)

 

 

CAN/COULD

We use can to express: possibility, ability, permission, offers, and requests.

The same morphological rules which apply to must, also apply to can and could (No –s, no perfect form, followed by a bare –inf. etc.)

-Possibility

Can expresses a GENERAL possibility.

Can gases freeze? (Is it possible, theoretically, for them to freeze?)

Could can be used as a past form of can and express past possibility (Up until 10 year ago, you could actually see kids playing outside instead of just sitting and watching TV.)

This is also the case in reported speech.

While can and could don't have perfect forms, a special construction: could have +past participle is used to refer to situations which were possible but did not happen, or even to express criticism (You could have told me you were going out tonight) (Why did you go out all alone at that hour? Somebody could have kidnapped you)

 

Can is often used to talk about the choices that somebody has.

(You can borrow the money from your family, work for the trip, or you can forget about the whole thing and stay at home)

Can is used in questions and negatives to express logical possibility. (See this above, under MUST)

 

-Ability

Can is used, again, to talk about GENERAL ability, something that somebody was able to do at any time. (I can swim. I can speak English). Could is used as a past form of could to express this general possibility. To say that somebody was able to do something at any time (When I was little, I could hold my breath for as long as a minute and a half).

NOTE THE DIFFERENCE BETWEEN CAN/COULD AND WAS ABLE TO. To say that somebody succeeded in doing something on one occasion, we use WAS ABLE TO and NOT could (The firemen were able to put the fire under control)

 

Generally, could is more tentative(less certain) than can regardless of whether it is used as a means of expressing possibility or some other meaning, and it is used when we want to sound less certain about something.

 

-Permission

Can and could are used to ask for permission. Again, could is more polite and tentative than can (Could I borrow your book?). But to give permission, we use can (precisely because could is polite and indicates respect) (Of course you could)

 It is possible for Can and could to be used to talk about the permission that has already been given and about things that are allowed by rules or laws. (When I was a kid, I could stay up until eleven). Again, for permission on one particular occasion, we use was allowed to (Yesterday, Peter was allowed to stay up until 11)

 

-Requests, orders, offers

Could you lend me five pounds? (In requests and orders, could is used to sound more polite.)

In offers, could sounds less definite than can (Could I carry your bag/Can I carry your bag?)

 

MAY/MIGHT

It has no –s in the third person singular

Questions are formed without do

It has no infinitives or participles

-Possibility/probability

We use may and might to talk about possibility. (I think Labour is going to win. You may be right).

Note that might IS NOT a past form of may, but only a more tentative form.(Although it IS used in indirect speech after a past verb of reporting as an equivalent of both may and might).

May is used to talk about typical occurrences. This is common in scientific language. (After having a baby, a woman may suffer from depression for several months)

 

May is not normally used in negative questions about probability

*May you go camping this summer?

 It is possible for might (but not may) to have a conditional meaning

(If you went to bed for an hour, you might feel better)

 

As with must and could, it is possible to combine may and might with have to form a structure that expresses that something was possible in the past

(Jean’s late. She might have missed her train.)

 

We cannot use may and might to express a general possibility.

 

-Permission

We can use May to give or ask for permission.

May I go out?

Yes you may

 

However, it is not possible to use may when talking about permission which has already been given, the freedom which people have or rules and laws. We use can or could instead. (Might is used in this sense ONLY in reported speech to report permission.)

*When I was a kid I might stay up late.

 

May is used to express wishes and hopes.

May the force be with you!

May you both be very happy.

 

Also, to express requests and suggestions, we can use might (because it is more tentative and polite than may)

You might see if John’s free this evening.

 

WILL (See footnote number 1)

WOULD

We use would to express a past habit.

(When she was old she would sit in a corner talking to herself for hours)

Would is used as a more tentative form of will in requests, offers.... (See footnote 1)

Would is also used in indirect speech with a past verb of reporting to backshift will.

(She said she would be here.)

 

SHOULD

Also has no –s in the third person singular

Questions are formed without do.

 It has neither infinitives nor participles.

As all other modals, it is followed by a bare infinitive

 

Should expresses a duty or obligation. We use it to talk about what is the right thing to do, and we can also use it to give advice. .

Ought to is also used in this sense.[3]

 

People should drive more carefully.

If you have free time, you should use it to catch up on your work.

 

We can also use it to express probability. (Because something is logical or normal)

(Henry should be here soon. –He left home at 6.)

 

THE USE OF SHOULD IN SUBORDINATE CLAUSES

Should can be used in subordinate that-clauses after adjectives that express necessity, or importance of the action. (Necessary, vital, important, essential, eager, anxious....). In this construction should is called “The putative should”

Note that this sort of a construction can be solved with a subjunctive[4] and express the same meaning.

It is important that he be present at the meeting

It is important that he should be present at the meeting.

The company demanded that they report their property

The company demanded that they should report their property.

 

Because of its less definite meaning should and would are used in some conditional sentences (2^nd type and 3^rd type with have (would have)