Editing Friction (section)

==Fluid friction{{anchor|Fluid}}==
{{Main|Viscosity|Drag (physics)}}

Fluid friction occurs between [[fluid]] layers that are moving relative to each other. This internal resistance to flow is named ''[[viscosity]]''. In everyday terms, the viscosity of a fluid is described as its "thickness". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity. The less viscous the fluid, the greater its ease of deformation or movement.

All real fluids (except [[superfluid]]s) offer some resistance to shearing and therefore are viscous. For teaching and explanatory purposes it is helpful to use the concept of an inviscid fluid or an [[ideal fluid]] which offers no resistance to shearing and so is not viscous.