Which term refers to any discrete device or physical entity in an electronic system?

The term that refers to any discrete device or physical entity in an electronic system is "Component." In electronics, a component can be anything from a resistor, capacitor, diode, or integrated circuit, all of which serve specific functions within a circuit. Components are the building blocks of electronic systems, allowing for the development and implementation of complex functionalities.

While "Device" can sometimes be used interchangeably with "Component," it generally refers to an assembly of components which work together to achieve a broader function. "Apparatus" usually implies a more complex setup or system, often related to experimental setups in scientific contexts rather than the individual parts within an electronic system. Lastly, "Circuit" refers to the complete path through which electricity flows, composed of various components, but does not denote individual entities.