Word Distinction: Objects for Doing Jobs

Device is a general word for any man-made object used for doing work, and is generally used when there is no suitable particular word:
a device for catching mice
I had no idea how this device worked.
A gadget is a small and perhaps unusual device for doing a particular job:
a clever little gadget for opening bottles
A machine usually uses power and is not worked directly by hand:
the machines in the factory
Electrical machines used in the home (such as washing machines) can also be called appliances.
An instrument is an object used to help in exact or difficult work, usually without power:
medical instruments
A thermometer is a measuring instrument.
A tool is an object held in the hand, without power, and used for making things from wood, metal or other materials:
A hammer is one of a carpenter’s tools.
An implement is usually larger than a tool, and is used for other jobs:
A plough is an instrument used in farming.