ABILITY ( = possibility)
can/could I canít see you tomorrow, Iím busy.
At one time I could run a mile in 4½ minutes.
able to ( = emphasis) Yesterday I was able to finish my work by teatime.
(understood: s/he did, in fact, finish it)
NB Can you swim? ( = Have you learned how to swim?)
Are you able to swim? ( = Are you all right?)
may ( = perhaps) Donít go into his room. He may be asleep.
If you say that, he may get very angry.
( = permission) May I borrow your bicycle for the afternoon?
You may go now (more formal than: You can go now)
NB (past permission) At one time only men were allowed to vote ( = could)
might ( = less probable) Take this torch. You might lose your way in the dark.
( = hesitation, politeness) Might I possibly use your telephone?
( = casual request) You might drop these letters in the post on your way by.
( = rebuke) You might have let me know that you were coming.
NB idiom: Thereís only one piece left. We might as well finish it up.
B. MUST/HAVE TO
must (= necessity imposed by speaker) I must get on with my reading.
I think you must go and have your hair cut
(= deduction, supposition) Did I say that? I must have been out of my mind.
have to ( = imposed from outside) We have to be there at two oíclock
NB had to (= did in fact do it) We missed the bus and had to walk.
I had to get up at five to milk the cows
(= I did do it)
NB (indirect speech) ďI must clean the carĒ - He said that he had to clean the car.
better: He said he must clean the car.
C. OUGHT TO/SHOULD
( = right/morally right) No wonder you look pale. You ought to get more fresh air.
They ought not to have told her = They should not have told her.
to be to ( = plan, order) All right then. We are all to meet here at midnight. Agreed?
The minister said that there was to be a review of teachersí pay.
going to (= intention) Iím going to succeed! (= I will succeed)
(action on the way) He was going to have lunch with me, but his car broke down.
I think Iím going to be sick! (I feel it coming)
Look at those clouds. Itís going to rain.
He drives like a madman. Heís going to get killed one of these days.
be about to ( = soon) Oh, hello! I was just about to call you.
Note the differences in usage in the examples below:
a) I must see my dentist (my decision: my tooth hurts)
b) I am to see my dentist today (plan: Iíve made an appointment)
c) I have to see my dentist (I must keep the appointment, s/heíll charge me anyway)
d) Iím going to see my dentist (Iíve made up my mindÖ/ Iím already on my way)
e) Iím about to see my dentist (I will see him/her in a few minutes)
A. FUTURE I shall we shall
you will you will
he/she/it will they will
NB in colloquial speech 1st person shall is often replaced by will
B. MODAL (includes emotional coloring)
Subjectís impulse, will or desire = will: I will help you (my desire)
other than Sís impulse, will, wish = shall: Shall I help you? ( = is it your wish?)
determination: I will succeed next time! (my desire)
persistence: If you will eat so many cakes, youíll get a tummy-ache. (you decide)
willingness: He says he will agree to anything. So will I. (we are both willing)
promise: You shall have an electric train set for your birthday (I promise that youÖ)
request: What shall I do next? (One part of me asks my other self)
offer: Will you have a drink? Or shall my wife make you a nice cup of tea?