re·dun·dant / riˈdəndənt/ • adj. no longer needed or useful; superfluous: an appropriate use for a redundant church many of the old skills had become redundant. ∎  (of words or data) able to be omitted without loss of meaning or function. ∎  Engineering (of a component) not strictly necessary to functioning but included in case of failure in another component. ∎  chiefly Brit. (of a person) no longer employed because there is no more work available: eight permanent staff were made redundant.DERIVATIVES: re·dun·dant·ly adv.

redundant characterized by superfluity or excess. XVII. — L. redundāns, -ant-, pp. of redundāre overflow, etc., f. RED- + undāre (of the sea) be agitated, surge, f. unda wave; see -ANT.
So redundance, redundancy XVII. — L.