1 grammar
Can and could are modal auxiliary verbs (see modal auxiliary verbs: introduction-354).
a There is no -s in the third person singular.
She can swim very well, (not She cans-…)
b Questions and negatives are made without do.
Can you swim? (not Bo yott-can swim?)
I couldn’t understand her. (not I-didnrt could …)
c After can and could, we use the infinitive of other verbs, without to.
I can speak a little Arabic, (not 1-ean-to speak …)
Do you think she can still be working? It’s very late.
d Can and could have no infinitives or participles do not exist). When necessary, we use other words, for example forms of be able (see be able or be allowed see allow, permit and let).
I’d like to be able to stay here, (not … to can stay …)
You’ll be able to walk soon, (not You’ll can …)
I’ve always been able to play games well, (not I’ve always could …)
She’s always been allowed to do what she liked.
e Could is sometimes used as the past of can.
When I was younger I could play tennis very well.
However, it can also be used as a less definite or conditional form of can, referring to the present or future (see can and could 2: ability.6, 124.1,4-6).
Could I ask you something? (More polite than Can I… ?)
What shall we do this evening? can and could : introductioncan and could : introduction We could go and see a film.
I could get a better job if I spoke French. (= I would be able to …)
f Certain past ideas can be expressed by can or could followed by a perfect infinitive (have + past participle). For details, see can and could 2: ability.7, can and could 3: ability advanced points.5 and can and could 4: interpersonal uses permission, requests etc.7.
I don’t know where she can have gone.
That was dangerous – he could have killed somebody.
g Can has two pronunciations: a strong form /kasn/ and a weak form /ken/. Could has a strong form /kud/ and a weak form /kad/. The weak pronunciation is used in most cases. For more details of strong and weak pronunciations, see weak and strong forms.
h Contracted negative forms (see contractions) are can’t (pronounced /ka:nt/ in standard British English and /keent/ in standard American English) and couldn’t (/’kudnt/). Cannot is usually written as one word in British English.
2 meanings
Can and could are both used to talk about ability, to ask for and give permission, and to make requests and offers.
Can you speak French? (ability)
You can stop work early today, (permission)
Could I have some more tea? (request)
Can I help you? (offer)
Could
is also used to talk about the chances that something will happen, or is happening. Can is not used in this way.
It could rain this afternoon, (not It can rain this afternoon.)
Can’t
is not only used to talk about ability or permission; it can also express negative certainty (see must 2: deduction concluding that something is certain.2).
It can’t be true. (= It is not possible that it is true.)
With see, hear and some other verbs, can is used to give a kind of present progressive meaning.
I can hear the sea. (not / am hearing the sea.)
May
and might are often used in similar ways to can and could. For the main differences, see may and might 8: may/might and can/could.
For more information consult a good dictionary like Langman, Oxford, Merriam Webster, or Collins.
Add Comment