Q.E.D. (also written as QED) is an initialism of the Latin phrase quod erat demonstrandum, meaning “that which was to be demonstrated”. Literally, it states “what was to be shown”. Traditionally, the abbreviation is placed at the end of mathematical proofs and philosophical arguments in print publications, to indicate that the proof or the argument is complete.
“Q.E.D.” Wikipedia, June 21, 2026. https://en.wikipedia.org/wiki/Q.E.D.