The noun disparity means the unfair inequality between two or more things.
Synonyms are discrepancy, distinction, gap, or imbalance.
The word origins in 1550s. It comes from French (1590s) disparité meaning “quality of being unequal in rank, condition, etc.”, and from Medieval Latin disparitatem meaning “inequality”. It is derived from dis- meaning “not” plus paritas meaning “parity”.
Our city doesn’t have a great learning disparity between public and private schools.
The two couples have large disparity in their age.
The disparity between my expenses and revenue has been very obvious.