A diamond is a valuable gemstone that's often used to make expensive jewelry. You might admire your friend's diamond earrings, but secretly wonder if they're real.
An engagement ring is typically set with one or more diamonds. Diamonds used for jewelry are cut and polished, and they're evaluated for quality and price by weight, or carat, as well as by their cut, clarity, and color. Another kind of diamond is the geometrical shape, which is also seen on playing cards called diamonds, and echoed in the shape of a baseball field, also known as a diamond.