Viscosity is sometimes called cohesiveness of fluid. Again someone calls viscosity the intrinsic friction of fluid. Because the nature at viscosity force is almost that of friction. Friction opposes the relative motion between two solid bodies; on the other hand viscosity opposes the relative motion between different layers of the fluid. It does not work in case of static fluid. Friction does not depend on the area of the contact surface but viscosity depends on the area of the contact layers. Besides, viscosity depends on the velocity of the layers of the fluid and also on the distance of the layer from the stationary surface.
Cohesion or cohesive attraction or cohesive force is a physical property of a substance, caused by the intermolecular attraction between like-molecules within a body or substance that acts to unite them. Water, for example, is powerfully cohesive due to strong polarity induced by two hydrogen bonds in a tetrahedral pattern. Viscosity is a assess of the resistance to flow of a fluid being deformed by shear stress whereas cohesion is a physical property of a substance, caused by the intermolecular attraction between like-molecules within a body or substance. Infact, cohesion is one of the factors accountable for viscosity in a fluid.
