Word.ws English Dictionary

q.e.d.

/ˌkjuːiːˈdiː/US/ˌkjuˌiˈdi/

q.e.d. is the alternative letter-case form of Q.E.D..

Phrase capitalized: Q.E.D.

Q.E.D.

  1. (abbreviation, dated, initialism) 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 August 29, Mr. Ash, “A New and Easy Way of Demonstrating Some Propositions in Euclid”, in Philosophical Transactions: Giving Some Accompt of the Present Undertakings, Studies and Labours of the...
    • Now let any right line meet four harmonicals in A, C, B, D, and if those harmonicals be parallel, the thing is evident; but, if they intersect in V, draw ECF parallel to VD, the line most remote from C; then, by the first part, EC#61;CF, and AD#58;AC#58;#58;VD#58;EC or CF. Therefore...1803, “The Mathematical Repository, Nº 63”, in The Gentleman’s Diary, or The Mathematical Repository; an Almanack for the Year of Our Lord 1803: […], London: Printed for the Company of Stationers by...
  2. (broadly) 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, Diedrich Knickerbocker [pseudonym; Washington Irving], chapter IV, in A History of New York, from the Beginning of the World to the End of the Dutch Dynasty. […], volume I, New York, N.Y....
    • PROP[OSITION] VI. One substance cannot be produced by another substance. ¶ Demonst[ration]. In the preceding proposition we have seen that there cannot in the nature of things be two Substances of the same attribute, or that they have anything in common (by Prop. II.); and so (by Prop. III.) one...1870, Benedict de Spinoza [i.e., Baruch Spinoza]; R[obert] Willis, “[The Ethics.] Part I.—Of God.”, in Benedict de Spinoza; His Life, Correspondence, and Ethics, London: Trübner & Co., […], →OCLC...

Noun capitalized: Q.E.D.

Q.E.D. (plural Q.E.D.s)

  1. A certain fact or scenario that proves an argument or proposition; a justification.
    • We all go in for the dolce here except you, and you're such a patent machine for turning out Q.E.D.s by the dozen, that you can no more help working than the bedmaker can help taking my tea and saying the cat did it,[…]1867, Ouida [pseudonym; Maria Louise Ramé], “The General’s Match-making; or, Coaches and Cousinship”, in Cecil Castlemaine’s Gage, and Other Novelettes, London: Chapman and Hall, […], →OCLC, page 233
    • The same thing, I believe, that was lacking in Let Freedom Ring—lack of dramatic integration, lack of dramatic intensity, lack of all those elements, call them what you will, which make a play a play and not a tract, and certainly not a Q.E.D. thesis.1936 April, Nina Melville, “The Theatre”, in V[ictor] F[rancis] Calverton [pseudonym; George Goetz], editor, The Modern Monthly: An Independent Journal of Radical Opinion, volume IX, number 9, →OCLC...

Forms of q.e.d.

Phrase
alternative formQED
alternative formQ. E. D.
alternative formq. e. d.
alternative formq.e.d.
Noun
pluralQ.E.D.s

Origin of q.e.d.

From Late Latin QED, from Latin quod erat demonstrandum.

Questions about q.e.d.

What does q.e.d. mean?
Q.e.d. means used to indicate that an argument or proposition is proved by the existence of some fact or scenario.
What is q.e.d. the alternative letter-case form of?
Q.e.d. is the alternative letter-case form of Q.E.D..
What part of speech is q.e.d.?
Q.e.d. can be a phrase or a noun.
How do you pronounce q.e.d.?
Q.e.d. is pronounced /ˌkjuːiːˈdiː/ (UK).

Words near q.e.d. in the dictionary

  1. q. e. d.
  2. q. v.
  3. Q.931
  4. Q.A.C.
  5. Q.C.
  6. q.e.d.
  7. Q.E.D.s
  8. Q.E.F.
  9. q.g.
  10. q.i.d.
  11. q.s.

Source and license

Adapted from Wiktionary: q.e.d. (page history and authors); Q.E.D. (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

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Pronunciation audio from Wikimedia Commons, each file under its own free license: En-uk-QED.oga.

Cite this entry: “q.e.d..” Word.ws, https://word.ws/q.e.d.. Based on Wiktionary, CC BY-SA 4.0.