What does "fifth" mean?

Fifth: Consisting of one of five equal divisions of a thing. Fifth monarchy men (Hist.), a fanatical sect in England, of the time of the commonwealth, who maintained that there would be a fifth universal monarchy, during which Christ would reign on earth a thousand years. -- Fifth wheel, a horizontal wheel or segment above the fore axle of a carriage and beneath the body, forming an extended support to prevent careening.

Additional senses

  1. 2.The quotient of a unit divided by five; one of five equal parts; a fifth part.
  2. 3.(Mus.) The interval of three tones and a semitone, embracing five diatonic degrees of the scale; the dominant of any key.

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