Act, v. i.
  1. To exert power; to produce an effect; as, the stomach acts upon food.
  2. To perform actions; to fulfill functions; to put forth energy; to move, as opposed to remaining at rest; to carry into effect a determination of the will.
     He hangs between, in doubt to act or rest.   --Pope.
  3. To behave or conduct, as in morals, private duties, or public offices; to bear or deport one's self; as, we know not why he has acted so.
  4. To perform on the stage; to represent a character.
     To show the world how Garrick did not act.   --Cowper.
  To act as or To act for, to do the work of; to serve as.
  To act on, to regulate one's conduct according to.
  To act up to, to equal in action; to fulfill in practice; as, he has acted up to his engagement or his advantages.
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