I.
Function
a. Can
- To express a person or thing’s ability
to do something
- To express or ask for permission to do
something
- To describe the possibility that something
can happen
- To issue requests and offers
Could
- Indicating what someone or something was
able to do in the past
- Instead of can as a more polite way of
making a request or asking for permission
- To express a slight or uncertain possibility
- For making a suggestion or offer.
b. May
- To request, grant, or describe permission
- To politely offer to do something for
someone
- To express the possibility of something
happening or occurring
- To express a wish or desire that something
will be the case in the future
- Rhetorical device to express or introduce an
opinion or sentiment about something
Might
- To express an unlikely or uncertain
possibility
- Acts as a very formal and polite way to ask
for permission
- The past-tense form of may when asking
permission in reported speech
- To suggest an action, or to introduce two
differing possibilities
c. Must
- To express necessity
- To emphasize something positive that you
believe someone should do
- To rhetorically introduce or emphasize an
opinion or sentiment
- To indicate that something is certain or
very likely to happen or be true.
d. Will
- To express willingness or ability
- To make requests or offers
- To complete conditional sentences
- To express likelihood in the immediate
present
- To issue commands.
Would
- It is used in place of will for things that
happened or began in the past
- To create more formal or polite sentences
- To express requests and preferences
- To describe hypothetical situations
- To politely offer or ask for advice or an
opinion.
e. Shall
- To form future tenses
- To make requests or offers
- To complete conditional sentences, or to
issue maxims or commands
Should
- To politely express obligations or duties
- To ask for or issue advice, suggestions, and
recommendations
- To describe an expectation
- To create conditional sentences
- To express surprise
II.
Differences
a.
Can and Could
Could, of course, functions as the past
tense of can, and like other past forms, it sometimes simply indicates past
time: In those days there was no security and anybody could walk in, day or
night. But, like the past forms of other verbs, it can also indicate things
like tentativeness, indirectness, deference and a wish not to impose.
b.
May and Might
Right away we notice that might deals with
situations that are speculative or did not actually happen, i.e. hypothetical,
whereas may deals with situations that are possible or could be factual. An
easy way to express/remember this difference is that might suggests a lower probability
than does may. If something is very far-fetched, you probably want to use
might. You could say might is for things that are mighty far-fetched. The
second distinction, which is the more important of the two, between these two
words is that might is the past tense of may.
c.
Must and Have to
A key distinction between must and have to
can be found in the negative forms. Whereas You must go and You have to go can
be regarded as broadly the same in terms of meaning, You mustn’t go and you
don’t have to go are quite different, the first indicating that going is
prohibited in some way, or even dangerous, while the second implies an absence
of obligation or need.
d.
Will and Would
When we use “will”, it indicates an
intention to do something in a situation that is really possible or likely to
happen. However, when we use “would”, it indicates an intention to do something
in a situation that is only in our imagination or that is very unlikely to
happen.
e.
Shall and Should
Should on the other hand is commonly
considered as a past tense of ‘shall’; however it does not always act as such.
‘Should’ being a modal verb, changes usage depending on the context. A modal
verb gives more information about the function of the main verb that it
governs.
III.
Examples
Can and Could
a.
Jasmine can go to college in the fall
b.
I can’t live without you
c.
Aqila could speak several languages
d.
Jasmine could not be here at the party
May and Might
a.
The instructor may come to class late today
b.
You may leave when you have finished your exam
c.
The criminal might not have been caught, had you
not sounded the alarm
d.
Athallah might have called earlier, but Jasmine
was not home
Must and Have to/Had to
a.
It must be hard to work 60-hours a week
b.
Aqila must not be late for her appointment
c.
We use had to for this if we are talking about
the past
d.
Jasmine won’t to be in work today. She has to
see the doctor
Will and Would
a.
Athallah will go to his second period class
tomorrow
b.
Jasmine won’t study English tonight because she
has to work
c.
That would be nice
d.
Would you please call me later tonight?
Shall and Should
a.
Shall I call you on your mobile?
b.
Jasmine shall be punished if she don’t pay taxes
on time
c.
I told him that I should go to Jakarta the next
day
d.
It is very surprising that they should lose the
match
