Hydraulic efficiency refers to how effectively a hydraulic system converts input energy into useful work. It is typically expressed as a percentage, indicating the ratio of useful output power to the total input power. High hydraulic efficiency means that most of the energy is being used effectively, while low efficiency indicates energy losses, often due to friction or turbulence within the system. Factors affecting hydraulic efficiency include the design of components like pumps and valves, the viscosity of the fluid, and the overall system layout. Improving hydraulic efficiency can lead to reduced energy consumption and lower operational costs, making it an important consideration in systems such as hydraulic machinery and fluid power systems.