mech·a·nism (mĕkˈə-nĭzˌəm)

1. A machine or mechanical appliance.
2. The arrangement of connected parts in a machine.
3. A system of parts that operate or interact like those of a machine.
4. An instrument or a process by which something is done or comes into being.
5. The involuntary and consistent response of an organism to a given stimulus.
6. A usually unconscious mental and emotional pattern that dominates behavior in a given situation or environment.
7. The sequence of steps in a chemical reaction.
8. The philosophical doctrine that all natural phenomena are explicable by material causes and mechanical principles.