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Pronunciation: sub'sti-tu'shun


  1. In chemistry, replacement of an atom or group in a compound by another atom or group (substitution of H by Cl in CH4 to give CH3Cl).
  2. In psychoanalysis, an unconscious defense mechanism by which an unacceptable or unattainable goal, object, or emotion is replaced by one that is more acceptable or attainable; the process is more acute and direct, and less subtle, than sublimation.

[L. substitutio, to put in place of another]

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