A fitted sheet is a type of bed sheet that is designed to fit snugly over a mattress. It has elasticized corners that allow it to stay in place and prevent it from slipping off the bed during sleep. Fitted sheets are usually made of cotton or a cotton-blend fabric, which makes them soft and comfortable to sleep on. They are available in various sizes to match different mattress dimensions, such as twin, full, queen, and king. Fitted sheets come in a wide range of colors and patterns, allowing people to customize their bedding and match it with their bedroom decor.