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Pronunciation: in'di-ka'tor, -tor


  1. In chemical analysis, a substance that changes color within a certain definite range of pH or oxidation potential, or in any way renders visible the completion of a chemical reaction, litmus, phenolsulfonphthalein.
  2. An isotope that is used as a tracer.
  3. The labeled substance the distribution of which between reactants of a system is used to determine the amount of analyte present.

[L. one that points out]

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