. General: Semi or fully automated device that magnifies human physical and/or mental capabilities in performing one or more operations.
2. Mechanics: Device that makes mechanical work easier by overcoming a resistance (load) at one end by application of effort (force) at the other end.
3. Systems: Purposefully organized set of components whose interconnections and inner workings are known or apparent. The behavior of a properly functioning machine is entirely predictable: its present state determines its next state, and the same inputs always yield the same outputs.