May vs might - what's the difference?

Both express possibility, but might suggests a smaller chance, and may sounds more formal.

"It may rain later." - quite possible, neutral tone
"It might rain later." - possible, slightly less certain, more casual

In formal grammar, might is the past tense of may, but in modern spoken English most people use them interchangeably. The distinction that actually survives:

• May - permission (formal): "You may leave." "May I ask a question?"
• Might - hypothetical or unlikely: "I might go if I feel better." "She might have forgotten."

Use might have (not may have) for past things that didn't happen:
"If I'd studied harder, I might have passed." ✓
"If I'd studied harder, I may have passed." - technically incorrect, though often heard

In conversation, most people just use might for possibility. May survives mainly in formal writing, permission requests, and expressions like "may the best team win."

May = formal/written. Might = casual/spoken.