Viscosity is a liquid's (or more generally a fluid's) resistance to flow. In more every day terms, it may be though of as how thick a liquid is. Viscosity describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion. Liquids such as vegetable oil have a low resistance and so a low viscosity, while liquids like honey have a high resistance and so a high viscosity.