Percale is a kind of cotton cloth. It is woven in a simple, tight, plain way, so it feels smooth and cool, and people use it a lot for bed sheets and pillowcases. Shop labels often say “percale sheets” to mean this crisp cotton, not a heavy cloth and not a shiny one. It is more a shop-and-label word than a home word — you meet it when you buy bedding. Though actually, it is still just cotton; the name tells you the weave and the feel, not a different plant. A high number on the label is not the same thing as percale: percale is about how the threads are crossed, not only how many there are.