By Oxford Languages’ definition, a cup is “a small bowl-shaped container for drinking from, typically having a handle”; While a mug is “a large cup, typically cylindrical with a handle and used without a saucer.”

So, a mug is a type of cup that is bigger in size and capacity and has a straighter shape (though with the creative designs these days, it’s best not to base on shape alone)

A cup is usually paired with saucers; mugs are used alone.

While both cups and mugs are used to serve hot drinks, a cup is usually used for serving tea, while mugs are usually used for coffee.