incommutability

from WordNet (r) 3.0 (2006)

incommutability
    n 1: the quality of being not interchangeable

from The Collaborative International Dictionary of English v.0.48

Incommutability \In`com*mu`ta*bil"i*ty\, n. [L.
   incommutabilitas: cf. F. incommutabilit['e].]
   The quality or state of being incommutable.
   [1913 Webster]