0Fluid is anything which can flow.They are not capable of resisting the shear deformation cause to it because of the shear forces.
Both Gases And Liquids studied under fluid.
Now come viscosity:
Viscosity is the property of fluid which provides resistance to its flow.So actually the resistance given to the flow of fluid is called its viscosity.
Viscosity is mainly due to two reasons :
1. Cohesive Forces .
2.Molecular Momentum Transfer.
In case of liquids cohesive forces dominates the molecular momentum transfer ,so in liquids it is mainly due to cohesive forces.
But in case of gases the molecular momentum transfer is very high as compare to cohesive forces in the molecules of gas ,so here in gases the viscosity is mainly due to molecular momentum transfer.
Viscosity is divided into two categories:
1.kinematic viscosity.
2. Dynamic viscosity.
