The word ball has several meanings:

1. A round object used in games and sports. You might throw a baseball, kick a soccer ball, dribble a basketball, or hit a tennis ball over a net. Balls come in different sizes: a golf ball fits in your palm, while a beach ball might be bigger than your head. The round shape makes balls roll, bounce, and fly through the air in ways that make them perfect for play and competition.
2. A formal dance party where people dress up elegantly. At a ball, guests might wear gowns and suits and dance to orchestral music. Think of Cinderella at the prince's ball. These grand events have been popular for centuries, especially among wealthy families. Today, some schools still host formal dances called balls, like a Valentine's Ball or a Winter Ball.
3. To form something into a round shape. You might ball up a piece of paper before tossing it in the trash, or ball cookie dough in your hands before putting it on a baking sheet.

The phrase have a ball means to have a really fun time, like you might say, “We had a ball at the amusement park!”