use, usage

machine; machinery

easy / simple, uncomplicated / brief, light, short

(chiefly in mathematics, physics) for simplicity; for the sake of simplicity

ease / simplicity / lightness, brevity

use, utilize

器械: a device, an appliance, a mechanism / 機械: a machine, equipment, an apparatus / 器械: a utensil, a tool, an instrument / 器械: a tool for conducting a test or experiment or for measurement

something that has gone unused

reuse

user; consumer / employer