We can use can, could, and may for requests and permissions, but is there any difference between the meanings of the following three versions?

  1. May I go?
  2. Can I go?
  3. Could I go?
  • @Neeku how does the duplicate question help this OP? If anything, this question should be migrated to ELL English language learners – Mari-Lou A Aug 24 '14 at 5:00
  • @Neeku That isn’t really a duplicate: it doesn’t address may nor does it identify backshifting modals (may, can, will, shall > might, could, would, should) as a gentling mechanism for politeness. The first one is the most polite, although all May I requests really should be immediately followed by please. The second with can is dirt-common but a bit rude in some eyes: many schoolteachers won’t let you go if asked so brusquely. A coarse tone may appeal to uncouth libertines lacking manners, but the language deserves better—so does the person you’re asking. Could falls in between. – tchrist Aug 24 '14 at 5:00

Each of these modal auxiliary verbs has a variety of meanings. While may almost certainly indicates that the speaker is seeking permission, it could also be interpreted as pondering the possibility, so that the first question could be paraphrased as is it possible that I choose to go? That's pretty far fetched though.

The other two are the present and past tense of the same word. Again, the most likely interpretation of these questions is asking permission, but they also readily allow an interpretation of possibility. They may even suggest ability, but this meaning would be more likely if the question was about someone or something else.

The past tense could admits a conditional meaning or may simply be more polite.

  • Good. I'd just add that 'May I go' sounds very formal (perhaps to the point of sounding faintly ridiculous) nowadays. – Edwin Ashworth Aug 23 '14 at 21:45

One definition of "could" is past tense of "can," but I don't think "could" is past tense here. "Could I go?" clearly refers to future action. See https://en.wiktionary.org/wiki/could

  • Tense and time are not completely bound up together. Past tense verbs usually have a past-time reference, but they don't need to. Often they are conditional, such as "if you went there tomorrow...". – Brett Reynolds Aug 24 '14 at 17:31

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