# What does QED mean? **URL:** \ **Category:** Factual Questions\ **Created:** [May 17, 2001, 7:28am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702 "2001-05-17T07:28:15Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Cisco](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Cisco](https://boards.straightdope.com/u/Cisco)\ **Post date:** [May 17, 2001, 7:28am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/1 "2001-05-17T07:28:15Z")
Couldn’t find anything about this by searching, it’s not in Merriam-Webster either. Thanks. ---
**Author:** ![Celyn](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@Celyn](https://boards.straightdope.com/u/Celyn)\ **Post date:** [May 17, 2001, 7:38am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/2 "2001-05-17T07:38:36Z")
From Dictionary of Difficult Words: [http://www.lineone.net/dictionaryof/difficultwords/d0010815.html](http://www.lineone.net/dictionaryof/difficultwords/d0010815.html) [quote] _quod erat demonstrandum ‘which was to be demonstrated’ (abbr. Q.E.D.). quod erat faciendum, ‘which was to be done’ (abbr. Q.E.F.). [/quote_ ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [May 17, 2001, 1:27pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/3 "2001-05-17T13:27:57Z")
Or **Q** uantum **E** lectro **D** ynamics ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [May 17, 2001, 1:33pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/4 "2001-05-17T13:33:20Z")
The use of the phrase and the abbreviation comes from classic geometry proofs. A student was given certain axioms as starting points and a hypothesis, and then required to develop a logical chain of reasoning to prove the hypothesis. If the student successfully proved the hypothesis, the student or professor would write “Quod erat demonstrandum” or “Q.E.D.” at the end of the proof. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [May 17, 2001, 1:53pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/5 "2001-05-17T13:53:24Z")
It’s latin for “there you go.” ---
**Author:** ![astorian](https://avatars.discourse-cdn.com/v4/letter/a/ad7895/32.png) [@astorian](https://boards.straightdope.com/u/astorian)\ **Post date:** [May 17, 2001, 1:53pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/6 "2001-05-17T13:53:47Z")
Literally, “quod erat demonstrandum” means “what had (yet) to be proven.” The implication is, “a minute ago, my point had yet to be proven, but now it HAS been proven.” It’s become a snobbish way of saying, “There! See? I told you so!” ---
**Author:** ![Olentzero](https://avatars.discourse-cdn.com/v4/letter/o/90ced4/32.png) [@Olentzero](https://boards.straightdope.com/u/Olentzero)\ **Post date:** [May 17, 2001, 2:18pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/7 "2001-05-17T14:18:03Z")
Let’s not forget QED’s two siblings: **Q** uod **E** rat **F** aciendum, “that which was to be done” **Q** uod **E** rat **I** nveniendum, “that which was to be found” God knows exactly what situations they could be used in, but I live for the day when I may do so. 🙂 ---
**Author:** ![G.B.H.Hornswoggler](https://avatars.discourse-cdn.com/v4/letter/g/c67d28/32.png) [@G.B.H.Hornswoggler](https://boards.straightdope.com/u/G.B.H.Hornswoggler)\ **Post date:** [May 17, 2001, 8:05pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/8 "2001-05-17T20:05:39Z")
Or, as my old Calculus teacher put it: **Q** uite **E** asily **D** one (why, yes, he _was_ a bit full of himself…) ---
**Author:** ![Bill\_H](https://avatars.discourse-cdn.com/v4/letter/b/a5b964/32.png) [@Bill\_H](https://boards.straightdope.com/u/Bill_H)\ **Post date:** [May 18, 2001, 4:13am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/9 "2001-05-18T04:13:37Z")
“Oh, you speak French” ---
**Author:** ![robinh](https://avatars.discourse-cdn.com/v4/letter/r/b77776/32.png) [@robinh](https://boards.straightdope.com/u/robinh)\ **Post date:** [May 18, 2001, 12:25pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/10 "2001-05-18T12:25:39Z")
In my high school geometry class we had the option of ending our proofs with either QED or W[sub]5[/sub]. ( **W** hich **W** as **W** hat **W** e **W** anted) ---
**Author:** ![MilTan](https://avatars.discourse-cdn.com/v4/letter/m/71e660/32.png) [@MilTan](https://boards.straightdope.com/u/MilTan)\ **Post date:** [May 18, 2001, 10:16pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/11 "2001-05-18T22:16:07Z")
I always preferred **Q** uit, **E** nough **D** one. ---
**Author:** ![ModernRonin2](https://avatars.discourse-cdn.com/v4/letter/m/c37758/32.png) [@ModernRonin2](https://boards.straightdope.com/u/ModernRonin2)\ **Post date:** [May 19, 2001, 1:38am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/12 "2001-05-19T01:38:30Z")
“Quickly Ends Dat”. ;] -Ben ---
**Author:** ![Daemon](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@Daemon](https://boards.straightdope.com/u/Daemon)\ **Post date:** [May 19, 2001, 5:52am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/13 "2001-05-19T05:52:11Z")
Queer Erotic Dreams. QED. ---
**Author:** ![Piell](https://avatars.discourse-cdn.com/v4/letter/p/34f0e0/32.png) [@Piell](https://boards.straightdope.com/u/Piell)\ **Post date:** [May 19, 2001, 5:39pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/14 "2001-05-19T17:39:27Z")
Quietly Elvis Died. Quickly Everyone Ducked. ---
**Author:** ![Amedeus](https://avatars.discourse-cdn.com/v4/letter/a/9de0a6/32.png) [@Amedeus](https://boards.straightdope.com/u/Amedeus)\ **Post date:** [May 19, 2001, 6:37pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/15 "2001-05-19T18:37:23Z")
Qualifying Educational Data From: [Acronym Finder](http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=QED) ---
**Author:** ![quasar](https://avatars.discourse-cdn.com/v4/letter/q/48db29/32.png) [@quasar](https://boards.straightdope.com/u/quasar)\ **Post date:** [May 19, 2001, 6:54pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/16 "2001-05-19T18:54:09Z")
**Quantum ElectroDynamics?** Can someone please elaborate? I know Richard Feynman won his Nobel Prize for his work in the development–independently of others, I believe–of this field of study, yet I must confess my ignorance regarding its nature and grasp. Q.E.D. (Quasar Exits Dabuilding) 🙂 ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [May 19, 2001, 7:18pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/17 "2001-05-19T19:18:43Z")
Working as a consultant I once wrote a project for cost accounting and management. At one point it was necessary to prove that a certain figure was indeed equivalent to another figure. So I wrote the proof and, at the end of the two pages I wrote Q.E.D. I thought my boss would appreciate my elegant demonstration as weel as my culture in using such an elegant ending. Instead, when he saw it, he said “what the hell is _this_?” I tried to explain “quod erat demostrandum” but he just snapped “it means ‘rest in peace’, get rid of it”… and so I did. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 19, 2001, 9:59pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/18 "2001-05-19T21:59:13Z")
**quasar** : Simply put, Quantum Electrodynamics is the quantum field theory of electromagnetism. In classical electromagnetism, you just treat the fields as smooth, continuous quantities: You can say, for instance, that the electric field due to a point charge is exactly k[sub]e[/sub]q/r[sup]2[/sup]. Of course, once you get down to the quantum level, charged particles interact by exchanging other particles (specifically photons), and the electric and magnetic “fields” are made up of a bunch of these virtual photons. QED is the theory which describes electromagnetism in these terms. And **sailor** , what did you expect? If he had any clue about anything, he wouldn’t be in management. ---
**Author:** ![Bill\_H](https://avatars.discourse-cdn.com/v4/letter/b/a5b964/32.png) [@Bill\_H](https://boards.straightdope.com/u/Bill_H)\ **Post date:** [May 19, 2001, 10:12pm UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/19 "2001-05-19T22:12:05Z")
Just so no one thinks I’m a complete idiot, my post above was actually a relevant line from a Thomas Dolby song. It’s funny if you’re in that lower .01% of the population with me. ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [May 20, 2001, 1:47am UTC](https://boards.straightdope.com/t/what-does-qed-mean/65702/20 "2001-05-20T01:47:51Z")
**sailor** , that’s pretty funny. Lord only knows what he would have made of _ipso facto._ “Whaaat, you callin’ me fat now?” 😃