Modal: May

May is the modal of formality and measured possibility. It sits above can and could on the politeness scale and operates in two primary domains: asking and granting permission, and expressing that something is possible but not certain.

For permission, may is the most polite and formal choice. May I borrow your pen? shows respect and deference in a way that Can I borrow your pen? does not. The traditional rule many learners are taught — "use may for permission, can for ability" — reflects this formality distinction rather than a hard grammatical rule. In granting permission, may again sounds formal and official: You may enter now. Compare the ladder: can (informal) → could (polite) → may (formal) → might (very formal).

For possibility, may expresses that something could be true but the speaker is not certain. She may be at home means there is a reasonable chance, perhaps fifty-fifty. May suggests slightly more certainty than might — she may be at home sounds a touch more probable than she might be at home, though the difference is subtle and many speakers use them interchangeably.

May is also the modal of wishes, especially in formal or ceremonial contexts. By inverting the word order — placing may before the subject — you create a blessing or hope: May you have a long and happy life, May the best team win. This construction is elegant and somewhat literary, common at weddings, graduations, and formal toasts.

The negative form is may not. The contraction mayn't exists but is so rare that even native speakers rarely use it; in negative questions, can't is preferred. May also leans on might for its past-tense needs in reported speech: She said she might arrive late. Where can is everyday and direct and might is tentative, may occupies the dignified middle — the modal you reach for when you want to sound both polite and precise.