A bed sheet is a piece of fabric used to cover a mattress, providing a comfortable surface for sleeping. Typically made from materials like cotton, polyester, or linen, bed sheets come in various sizes, including twin, full, queen, and king, to fit different mattress dimensions. They can be plain or patterned, allowing for personal expression in bedroom decor. Bed sheets are usually part of a larger bedding set, which may include pillowcases, comforters, and bed skirts. Regular washing is essential for maintaining hygiene, as bed sheets can accumulate dust, sweat, and allergens over time.