Source : Webster's Revised Unabridged Dictionary (1913)

Commutability \Com*mu`ta*bil"i*ty\, n.
   The quality of being commutable.

Source : WordNet®

commutability
     n 1: exchangeability by virtue of being replaceable [syn: {replaceability},
           {substitutability}]
     2: the quality of being commutable [syn: {transmutability}]