The noun /naʊn/ pronounced /kæ̃nz/ (cans) refers to what in French are called boîtes de conserve. Go figure. :) English "boxes" refer to many things, but not to cylinders. It was a Frenchman, Nicolas Appert, who invented the process of canning, which helped provision Napoleonic troops in the War of 1812.
- Pronounced most often in its weak form: /kn/ or /kən/.
- The strong form is /kæ̃n/ (The tilda over the ae symbol means it is nasalized: Parlez-vous kwæ̃kwæ̃?) (Cf. la voyelle française de "ben", si aigu au Canada: bɛ̃)
- The negative contraction can't is pronounced kæ̃t in American English.
A little history and comparison is helpful here. German kennen and French connaître (to be acquainted with), like English know and Greek gnosis all have the same root sounds.
One possible synonym / periphrastic of can is know how to.
- Manon can't cook, but she does know how to sing opera.
One of the most important/frequent periphrastics in English is be able to. bɪjeɪbəltə
Can is used in the present tense only, though it can refer to the future (which is not a tense).
- I can come tomorrow.
- I can't be there next week.
It is possible, but not necessary to use will be able to instead of can to speak of the future.
- I'll be able to come tomorrow.
- I won't be able to be there next week.
Could can also be used for a hypothetical future. However, strangely, couldn't cannot be used for a negative hypothetical future.
- I could come to your office once the lockdown ends.
I couldn't come to your office once the lockdown ends.
- I could send it to you by email. (if you would like)
I couldn't send it to you by email.<-- necessarily interpreted as the past tense (je ne pouvais pas te l'envoyer par mél.)
In the past (and the conditional or "future of the past") "be able to" may be used.
- was(n't)/were(n't) able to
- would(n't) be able to
Couldn't can also be used for the past tense. However, could is not generally used for the past tense (except with the perfect infinitive, or with focusing adverbs like "only" or "even")
- I couldn't come to your office in April 2020 because of the lockdown.
- I could only see my clients using Zoom, Whatsapp or Skype in April 2020.
I could see my clients yesterday.
- The pandemic could have been worse (if there hadn't been a lockdown).
reminder: bɪjeɪ bəl tə (and eɪ = the letter A)
- We won't be able to...
- Will you be able to... ?
- They weren't able to...
- Wasn't she able to... ?
- Wouldn't you be able to... ?
syntax & semantics
- cannot be combined with (preceded or followed by) other modal verbs or "to"
- can be followed by the verbal base / bare infinitive (or nothing)
- has at least two main meanings (one "radical" (capability), one "epistemic" (possibility))
|can||could||capability / possibility|
|will||would||future / certainty / volonté|
|shall||should||value judgement / necessity|
|may||might||authorization / probability|
|must||logical necessity / certainty|