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The phrase quod erat demonstrandum is a translation into Latin from the Greek ὅπερ ἔδει δεῖξαι (hoper edei deixai; abbreviated as ΟΕΔ). The meaning of the Latin phrase is "that [thing] which was to be demonstrated" (with demonstrandum in the gerundive).
The earliest known use of the phrase quod erat demonstrandum is in the early 1600s. OED's earliest evidence for quod erat demonstrandum is from 1614, in the writing of William Bedwell, Arabist and mathematician.
Q.E.D. or QED is an initialism of the Latin phrase Latin: '''quod erat demonstrandum''', meaning "that which was to be demonstrated". Literally it states "what was to be shown".
These initials stand for the Latin quod erat demonstrandum meaning, ‘what was to be demonstrated’. It was coined by Euclid in Greek c. 300 BC but it is better known in its Latin translation. The expression QED is typically used by mathematicians and philosophers to conclude proofs and arguments.
Oct 8, 2018 · The Latin quod erat demonstrandum literally means “what was to be demonstrated.”. It is actually a transliteration of a phrase ancient Greek mathematicians placed at the end of logical proofs—a kind of stamp that says “I proved what I set out to. Usage for the abbreviation Q.E.D. is found from the 17th century.
It was invented by Aristotle (384–322 B.C.) in Athens, and recorded in a group of writings known as the Organon. In one of these works, the Prior Analytics, Aristotle attempted to provide a complete analysis of the valid forms of reasoning.
The phrase originates from ancient Greek mathematics and philosophy, where demonstrating conclusions through rigorous proof was essential. In modern usage, Q.E.D. is still seen in academic writing, especially in mathematics, to affirm the validity of a proof.
