Fluid mechanics is concerned with the study of forces and movements of liquids and gases. Both substances are continua whose elements can easily move against each other. They are grouped together under the term fluid.
In fluid mechanics, the measurement of temperature, pressure and flow rate are of particular interest.
Hydrostatics is the study of fluids at rest.
Hydrodynamics is concerned with the study and description of fluids in motion. The main emphasis is the teaching of the conservation laws of mass, energy and momentum.