The noun 床单 (chuángdān) means "bedsheet" or "bed linen." Beyond its everyday meaning, it can appear in dramatic contexts — for example, people tying bedsheets together as an improvised rope. It is a compound of 床 (bed) and 单 (sheet).
我每周都会换一次床单。
wǒ měi zhōu dōu huì huàn yí cì chuángdān.
I change the bed sheets once every week.
这套新床单的颜色很好看。
zhè tào xīn chuángdān de yánsè hěn hǎokàn.
The color of this new set of bed sheets is very nice.
妈妈把洗好的床单晾在了阳台上。
māma bǎ xǐ hǎo de chuángdān liàng zài le yángtái shàng.
Mom hung the freshly washed bed sheets on the balcony to dry.