Source : Webster's Revised Unabridged Dictionary (1913)

Interchangeability \In`ter*change`a*bil"i*ty\, n.
   The state or quality of being interchangeable;
   interchangeableness.

Source : WordNet®

interchangeability
     n : the quality of being capable of exchange or interchange
         [syn: {exchangeability}, {interchangeableness}, {fungibility}]
         [ant: {unexchangeability}]