Hydraulics vs. Pneumatics — What's the Difference?

Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concerns gases.

Pneumatics (from Greek πνεῦμα pneuma ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases.

The physical science and technology of the static and dynamic behavior of fluids.

The study of the mechanical properties of air and other gases.

The engineering science that deals with practical applications where liquid is in motion and transmits energy.

The branch of mechanics that deals with the mechanical properties of gases

The hydraulic system of a vehicle or other machine.

The scientific study or knowledge of spiritual beings and their relations to God, angels, and human beings.

That branch of science, or of engineering, which treats of fluids in motion, especially of water, its action in rivers and canals, the works and machinery for conducting or raising it, its use as a prime mover, and the like.

That branch of science which treats of the mechanical properties of air and other elastic fluids, as of their weight, pressure, elasticity, etc. See Mechanics.

Study of the mechanics of fluids

The scientific study or knowledge of spiritual beings and their relations to God, angels, and men.

The branch of mechanics that deals with the mechanical properties of gases