How is hydraulics best described?

Hydraulics is best described as fluid energy because it primarily focuses on the mechanical properties and behavior of liquids. In hydraulic systems, liquids are used to transmit force and energy through pipes and machinery, allowing for the control and movement of heavy loads with relatively low effort. The term "fluid energy" encompasses the kinetic and potential energy that can be harnessed from the fluid under pressure.

While "liquid mechanics" could also be relevant, it is a broader term that encompasses the study of liquids without specifically highlighting their energy use in practical applications. "Gas dynamics" pertains specifically to the behavior of gases under various conditions, which is not applicable to hydraulics. Similarly, "thermal transmission" relates to heat flow, which is not a central concept in hydraulic systems. Thus, describing hydraulics as fluid energy accurately captures the essence of how hydraulic systems operate and the role of fluids in energy transmission.