What defines a machine that receives its power from liquid pressure?

A machine that operates using liquid pressure is defined as hydraulic. This terminology is derived from the mechanics of moving fluids, particularly liquids, which are used to transmit force and perform work. In hydraulic systems, liquid pressure is used to create movement and control the operation of machinery.

Hydraulic systems are essential in many applications, including construction machinery, automotive systems, and industrial equipment. They provide several advantages, such as the ability to generate large amounts of force with relatively small components due to the incompressible nature of liquids.

In contrast, pneumatic systems utilize gases under pressure for operation, while mechanical systems derive their power primarily from physical components without the need for hydraulic or pneumatic assistance. Electrical machines convert electrical energy into mechanical work, which is a different form of powering machinery. Thus, hydraulic is the term that specifically refers to systems driven by liquid pressure.