The viscosity of the fluid is its resistance to a change in form or motion of neighbouring sections relative to each other. Viscosity signifies resistance to flow.
Fluidity, a measurement of an ease of flow, is the reciprocal attribute of viscosity.
The unit for viscosity is Newton-second per square metre, which would be generally written in SI units as pascal-second.
The viscosity in liquids drops fast as temperature rises, but the viscosity in gases rises as temperature rises. As a result, liquids flow more freely when heated, and gases flow more slowly.
When fluids are employed in lubrication and carried in pipelines, viscosity is a crucial element in determining the pressures which must be overcome. It regulates liquid flow in operations like spraying, injection moulding, & surface coating.