su·per·e·rog·a·to·ry /ˌsupərəˈrɒgəˌtɔri, -ˌtoʊri/

1. going beyond the requirements of duty.
2. greater than that required or needed; superfluous.

1585–95; < ML superērogātōrius. See supererogate, -tory

—Related forms
su·per·e·rog·a·to·ri·ly, adverb


“I willingly grant the scientist his three atoms,” said Ildefonse, “though in the strictest sense, two of these are supererogatory.”

Source: Tales of the Dying Earth by Jack Vance.