When it comes to the usage of modal verbs “could” and “may” for permission, there are subtle differences in their implications and formality levels:

1. “Could”:

– Implication: “Could” is often used to suggest a possibility or ability, making it somewhat more tentative or indirect compared to “may.”

– Formality: Although not as formal as “may,” “could” is considered polite and is commonly used in everyday conversations.

– Examples: “Could I use your phone?” or “Could you please pass me the salt?”

2. “May”:

– Implication: “May” is typically used to grant permission in a more direct and formal manner.

– Formality: “May” is considered more formal and is often used in written communication or formal situations.

– Examples: “You may leave the room now” or “May I have a moment of your time?”

Generally, “may” is used when a more formal or direct permission is being sought or given, especially in contexts where politeness and formality are important. On the other hand, “could” is used for slightly more tentative or polite requests in less formal situations.

Therefore, the choice between “may” and “could” for permission depends on the level of formality required in the situation and the tone you wish to convey in your request or response.