📒 used to say that something might exist, happen or be true, but you are not certain
📒 used with can/could to emphasize that you are surprised, annoyed, etc. about something
📒 used with could to ask somebody politely to do something
📒 used with can/could to say that somebody will do or has done as much as they can in order to make something happen
📒 used with negatives, especially can't/couldn't, to say strongly that you cannot do something or that something cannot or could not happen or be done