衛生紙
Most modern toilet paper in the developed world is designed to decompose in septic tanks, whereas some other bathroom and facial tissues are not. Wet toilet paper rapidly decomposes in the environment. Toilet paper comes in various numbers of plies (layers of thickness), from one- to six-ply, with more back-to-back plies providing greater strength and absorbency. Some people have a preference for whether the orientation of the roll on a dispenser should be "over" or "under".