The viscosity of a fluid is a measure of its resistance to deformation at a given rate. The SI unit of viscosity is the pascal-second. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the internal frictional force between adjacent layers of fluid that are in relative motion. For instance, when a viscous fluid is forced through a tube, it flows more quickly near the tube's axis than near its walls. This fluid animation shows a simulation of two fluids with different viscosities being poured into identical containers. The blue liquid on the left has a lower viscosity than the orange liquid on the right.Animation credit: Gvbox