IPA: //nʌnˈɛkwɪvələns//
KK: /nʌnˈɛkwɪvələns/
The state of being not equal or equivalent; a lack of equivalence between two or more things.
The nonequivalence of the two proposals led to a lengthy debate.
Nonequivalence → It is formed from "non-" (meaning not) and "equivalence" (from Latin "aequalis", meaning equal). The word describes a state of not being equal or equivalent.
Think of 'not' ('non-') being applied to 'equal' ('equivalence') — this helps you remember that nonequivalence means a lack of equality.