noun

• (within a machine or machinery) Any mechanical means for the conversion or control of motion, or the transmission or control of power.
• Any combination of cams, gears, links, belts, chains and logical mechanical elements.
• A group of entities, such as objects, that interact together.
• A mental, physical, or chemical process.
• Any process of, or system designed to manage useful energy conversion.
• (philosophy) The theory that all natural phenomena can be explained by physical causes.