Q.E.D.

Meanings

1. 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.
2. Used to indicate that an argument or proposition is proved by the existence of some fact or scenario.

1. A certain fact or scenario that proves an argument or proposition; a justification.

1. Alternative letter-case form of Q.E.D..

Etymology

From Late Latin QED, from Latin quod erat demonstrandum.