The word appliance has several different areas of meaning, all usually referring to a device with a narrow function:
One class of objects includes items that are custom-fitted to an individual for the purpose of correction of a physical or dental problem, such as prosthetic, orthotic appliances and dental braces.
Another class of objects includes items that accomplish routine household tasks, using electricity or some other energy input. These are grouped into two categories: small appliances and major appliances. Such items as toilets and sinks are not appliances, but plumbing fixtures, because they operate only with water and not with energy input.
A certain class of computer products, where the device has a specific function, and limited ability to configure.