Mech"an*ism (?), n. [Cf. F. mécanisme, L. mechanisma. See Mechanic.] 1. The arrangement or relation of the parts of a machine; the parts of a machine, taken collectively; the arrangement or relation of the parts of anything as adapted to produce an effect; as, the mechanism of a watch; the mechanism of a sewing machine; the mechanism of a seed pod.

2. Mechanical operation or action.

He acknowledges nothing besides matter and motion; so that all must be performed either by mechanism or accident.

3. (Kinematics) An ideal machine; a combination of movable bodies constituting a machine, but considered only with regard to relative movements.

• A machine.
  
• A group of parts performing a specific function in a machine.
  
• A group of objects that interact together.
  
• A mental, physical or chemical process.
  
• (Philosophy) A theory that all natural phenomena can be explained by physical causes.