billiard ball Directory References Discover Why Does the New Year Start on January 1? New Seven Wonders of the World The Largest Islands in the World Periods of American Literature 26 Decade-Defining Events in U.S. History 12 Novels Considered the “Greatest Book Ever Written” How Do Deserts Form? billiard ball billiards Ask the Chatbot a Question Learn about this topic in these articles:billiards In billiardsThe billiard balls, formerly made of ivory or Belgian clay, are now usually plastic; they each measure from about 21/4 to 23/8 inches (5.7 to 6 cm) in diameter, the larger balls being used in carom billiards.Read More