A fitted sheet is a type of bed linen designed to cover a mattress snugly. It has elastic corners that help it stay in place, preventing it from slipping off during the night. Fitted sheets come in various sizes, such as twin, full, queen, and king, to fit different mattress dimensions. Fitted sheets are typically made from materials like cotton, polyester, or a blend of both, offering comfort and durability. They are often used as the bottom layer of bedding, providing a smooth surface for sleeping. Many people choose to coordinate their fitted sheets with flat sheets and pillowcases for a cohesive look.