Meaning of characteristic function

char'acteris'tic func'tion

Pronunciation: [key]
— Math. Math.
  1. a function defined on a given set, having value 1 for every element of the set and value 0 for every element not contained in the set.
  2. See
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.