QED
See also: Q.E.D.
English
Pronunciation
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Etymology 1
From Late Latin q.e.d., from Latin q(uod) e(rat) d(emonstrandum).[1]
Phrase
(deprecated template usage) QED
- (mathematics, dated) Initialism of quod erat demonstrandum (“what had 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.
- 1999, William Dunham, “Euler and Analytic Number Theory”, in Euler: The Master of Us All (The Dolciani Mathematical Expositions; 22), [Washington, D.C.]: Mathematical Association of America, →ISBN, page 64:
- By Cases 1 and 2, we see that any finite collection of primes cannot contain all such primes. Thus there are infinitely many primes of this type. Q.E.D.
- (by extension) Used to indicate that an argument or proposition is proved by the existence of some fact or scenario.
Usage notes
When used to end a mathematical proof, QED is somewhat dated or traditional; modern textbooks often use the graphical symbol ∎ (the halmos or tombstone) instead. Other languages generally use a vernacular abbreviation, such as French CQFD (“ce qu'il fallait démontrer”).
Alternative forms
Related terms
Translations
placed at the end of a mathematical proof to show that the theorem under discussion is proved
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Noun
QED (plural QEDs)
- Some fact or scenario that proves an argument or proposition; a justification.
Alternative forms
Translations
fact or scenario that proves an argument or proposition — see justification
Etymology 2
From q(uantum) e(lectro)d(ynamics).[2]
Noun
QED (uncountable)
- (physics) (Partial) initialism of quantum electrodynamics.
- 2011, Brian Cox, Jeff Forshaw, “Interaction”, in The Quantum Universe: Everything that Can Happen Does Happen, London: Allen Lane, →ISBN, page 176:
- QED is the theory that explains how electrically charged particles, like electrons, interact with each other and with particles of light (photons). [...] Pretty much everything else – certainly everything you see and feel around you – is explained at the deepest known level by QED. Matter, light, electricity and magnetism – it is all QED.
Related terms
- QCD (“(partial) initialism of quantum chromodynamics”)
References
- ^ “Q.E.D., int. and n.1”, in OED Online , Oxford, Oxfordshire: Oxford University Press, December 2007; “QED, abbrev.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.
- ^ “QED, n.2”, in OED Online , Oxford, Oxfordshire: Oxford University Press, December 2007; “QED, abbrev.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.
Further reading
- Q.E.D. on Wikipedia.Wikipedia
- quantum electrodynamics on Wikipedia.Wikipedia
Anagrams
Latin
Phrase
QED
- QED (“quod erat demonstrandum”) Initialism of quod erat demonstrandum.
Descendants
- English: QED (“quod erat demonstrandum”)
Portuguese
Etymology
Phrase
Synonyms
Categories:
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- en:Mathematics
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