Viscosity is the thickness of a liquid. Water flows easily. Honey does not — that's why it has greater viscosity than water.
Viscosity, pronounced "vis-KOSS-ih-tee," tells you how sticky a liquid is. In the working of machines and car engines, viscosity is important. Thick oils and lubricants that have high viscosity, meaning they coat and cling, keep hard metal parts from wearing down as they rub together. Oils with dense viscosity keep machine parts from having too much friction and burning out.