Definitions of mechanism:

• noun:   the technical aspects of doing something

  Example: "A mechanism of social control"

• noun:   device consisting of a piece of machinery; has moving parts that perform some function
• noun:   (philosophy) the philosophical theory that all phenomena can be explained in terms of physical or biological causes
• noun:   a natural object resembling a machine in structure or function

  Example: "The mechanism of the ear"

• noun:   the atomic process that occurs during a chemical reaction

  Example: "He determined unique mechanisms for the photochemical reactions"