Q.E.D. /ˌkjuːiːˈdiː/noun 1phrase 2forms 1 noun1 •A certain fact or scenario that proves an argument or proposition; a justification. phrase2 •Used to indicate that an argument or proposition is proved by the existence of some fact or scenario.That this part of the world has actually been peopled (Q. E. D.) to support which, we have living proofs in the numerous tribes of Indians that inhabit it. — 1809 •Initialism of quod erat demonstrandum (“what was to be proved; what was to be demonstrated”): placed at the end of a mathematical proof to show that the theorem under discussion is proved.[A]fter the same manner S and U are proved to be equal, therefore the square of CB is equal to the square of the 2 other sides Q E D. — 1684 formsQ.E.D.s
