Derogation

The act of derogating, partly repealing, or lessening in value; disparagement; detraction; depreciation; -- followed by of, from, or to.

An alteration of, or subtraction from, a contract for a sale of stocks.

(law) the partial taking away of the effectiveness of a law; a partial repeal or abolition of a law; "any derogation of the common law is to be strictly construed"