Sorry I'm not a technical expert. Just a native speaker. If someone with more expertise could fill in my gaps? I use these interchangeably but with varying degrees of respect. Can I borrow this? - least formal, I use this for friends and family. Could I borrow this? - more formal than above, I use this for people I don't know or if I just want to raise the level of respect. May I borrow this? - more formal than above, I don't normally use this in my day-to-day but it's supposed to be proper English. It can be wrong vs. it could be wrong - both suggest that there is possibility of wrongness but the word "could" softens it slightly.