derogation

Etymology

From Old French derogacion (French dérogation), from Latin dērogātiō.

noun

1. An act which belittles; disparagement.
2. (law) The act of derogating; the temporary or partial nullification of a law.
   Two sets of Mk. 2 coaches hauled by Class 37s were introduced on peak Rhymney services during the summer. The coaches do not comply with the Persons with Reduced Mobility (PRM) standards and would therefore need a derogation to continue in passenger service after 31 December. 2019 October, Rhodri Clark, “TfW seeks PRM derogation for Class 37 sets”, in Modern Railways, page 87