What does the word duplication mean?

Usage examples for duplication

  1. For the first time in my life I feel the sweet certainty of duplication. – Phemie Frost's Experiences by Ann S. Stephens
  2. Have a procedure that prevents duplication of effort. – The Online World by Odd de Presno
  3. I instantly thought that they could be photographed, so as to show the duplication produced by the illusion. – Real Ghost Stories by William T. Stead