nonequivalence

/ ˌnɒnɪˈkwɪvələns /

noun

1. the relationship of being unequal or incomparable
2. logic
   1. the relation between two statements only one of which can be true in any circumstances
   2. a function of two statements that takes the value true only when one but not both of its arguments is true
   3. a compound statement asserting that just one of its components is true