General ability in the present to do something, or an informal request or permission granted.
- I can write a grammar book. George can sing better than his brother.
- Can I have the last cookie? Megan can use my book.
General ability in the past to do something, or an informal request or permission granted.
- Lester could play the piano when he was five.
- Could you pass the salt?
A formal request or permission granted, or a possibility, something that could or could not happen.
- May I go to the bathroom? Students may use a calculator on the test.
- I may go see the movie tonight, or I may wake up early tomorrow to see it.
A possibility, something that could or could not happen. Usually stronger possibility than may.
The library might allow students to bring in food.
Something that is a necessity either in the present or the future, a strong possibility, or a near certainty in the present or past.
- For the best result, you must mix the batter for five minutes.
- Andrew must be late.
- You must have left the tickets in the car.
Suggestions or advice, obligations or duties, or expectations.
- Everyone should drink water every day.
- The teacher should protect your personal information.
- Your food should arrive soon.
A certainty, request, or promise.
- If you don’t go to sleep now, you will regret it tomorrow.
- Will you go to Miranda’s party with me?
- Jamie will plan the wedding.
Polite requests or repeated actions in the past.
- Would you help me finish this pie? I would like some milk.
- Whenever Elias needed help with writing, he would visit his professor.