single word requests - What is the opposite of 'identity' in this case?

I am looking for a word that describes the exact opposite of identity.

I have this sentence that says The identity operator returns true if the operands are strictly equal.

In other terms is there a word for not strictly equal / strictly unequal?

There is an operator that does the opposite: The opposite word operator returns true if the operands are strictly unequal.

I tried to google the antonyms and such, but none of the proposed words match or satisfy this case in my opinion. Or did you see or do you think one them could be used?

• difference


• dissimilarity


• opposite


• non-identity


• other suggestions?

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Definitions for this case:

equal - only very few characteristics cannot be in common.

strictly equal - all characteristics are in common.

unequal - only very few characteristics can be in common.

not strictly equal - none of the characteristics are in common.

I don't want it to be a Math question. They use symbols not words.