# Ok, What is Q.E.D.? Never saw it B4... **URL:** \ **Category:** Factual Questions\ **Created:** [June 17, 2005, 8:12am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678 "2005-06-17T08:12:12Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [June 17, 2005, 8:12am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/1 "2005-06-17T08:12:12Z")
Besides someone’s handle on the SDope, what is QED? I just saw it used as if it refers to some Latin, legal phrase, I wag? Maybe I should know, but then again, how many people realy understand i.e. vs. e.g.? …Maybe it’s like QB VII? 88 C in the N.S… - Jinx ---
**Author:** ![Pedro](https://avatars.discourse-cdn.com/v4/letter/p/919ad9/32.png) [@Pedro](https://boards.straightdope.com/u/Pedro)\ **Post date:** [June 17, 2005, 8:30am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/2 "2005-06-17T08:30:47Z")
It is an old abbreviation for “quod erat demonstrandum”, which is Latin for “as we wished to show”. It’s used to conclude math proofs. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 17, 2005, 8:32am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/3 "2005-06-17T08:32:03Z")
It’s an abbreviation of a latin phrase, used to indicate that a conclusion has been reached, or a point proven; more details [here](http://mathworld.wolfram.com/QED.html). ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [June 17, 2005, 9:40am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/4 "2005-06-17T09:40:02Z")
> [@Jinx](#): > > but then again, how many people realy understand i.e. vs. e.g.? I think _i.e._ is for explanations, and _e.g._ is for examples. And I think if you’re writing a college paper, put them in italics, because they’re Latin. If not, someone please tell me, because it’s really annoying to have to do that. Just think of QED as “There, I told you so,” in Latin. ---
**Author:** ![pseudotriton\_ruber\_ruber](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@pseudotriton\_ruber\_ruber](https://boards.straightdope.com/u/pseudotriton_ruber_ruber)\ **Post date:** [June 17, 2005, 9:50am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/5 "2005-06-17T09:50:47Z")
[QUOTE=Pedro] “quod erat demonstrandum”, which is Latin for “as we wished to show”. QUOTE] I’ve got almost no Latin, so you may be correct, but I’ve always translated it “Thus it is demonstrated that…” Anyone remember the National Lampoon bit about 'Rasmus and 'Quinas?: “Q.E.D., you is shit!” ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [June 17, 2005, 10:16am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/6 "2005-06-17T10:16:23Z")
> [@Pedro](#): > > It is an old abbreviation for “quod erat demonstrandum”, which is Latin for “as we wished to show”. It’s used to conclude math proofs. It’s Latin for “which was to be demonstrated”. ---
**Author:** ![aldiboronti](https://avatars.discourse-cdn.com/v4/letter/a/9fc348/32.png) [@aldiboronti](https://boards.straightdope.com/u/aldiboronti)\ **Post date:** [June 17, 2005, 10:37am UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/7 "2005-06-17T10:37:59Z")
Yes, it was appended to the theorems of Euclid, as was also the companion initialism, **QEF** , “_Quod erat faciendum_”, ‘which was to be done’. ---
**Author:** ![twickster](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@twickster](https://boards.straightdope.com/u/twickster)\ **Post date:** [June 17, 2005, 12:11pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/8 "2005-06-17T12:11:16Z")
> [@guizot](#): > > I think _i.e._ is for explanations, and _e.g._ is for examples. And I think if you’re writing a college paper, put them in italics, because they’re Latin. If not, someone please tell me, because it’s really annoying to have to do that. Yes, you have the meaning correct. i.e. is short for “id est” (it is) – e.g. for “exempli gratia” (for the sake of example). I’ve never seen them italicized. They’re standard abbreviations, even though from the Latin – like etc. (et cetera). ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [June 17, 2005, 12:11pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/9 "2005-06-17T12:11:43Z")
> [@Jinx](#): > > Maybe I should know, but then again, how many people realy understand i.e. vs. e.g.? Simple enough: i.e. = that is. e.g. = for example. ---
**Author:** ![Scarlett67](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scarlett67/32/7387_2.png) [@Scarlett67](https://boards.straightdope.com/u/Scarlett67)\ **Post date:** [June 17, 2005, 12:24pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/10 "2005-06-17T12:24:03Z")
> [@RealityChuck](#): > > Simple enough: i.e. = that is. e.g. = for example. Easy enough to look up (although I know that **RealityChuck** didn’t have to 🙂 ), but many people still don’t understand the conceptual distinction: “that is” introduces a clarification or further definition, while “for example” (strangely enough) introduces examples of what is being discussed. I routinely change these to English when copyediting general text. ---
**Author:** ![Cliffy](https://avatars.discourse-cdn.com/v4/letter/c/59ef9b/32.png) [@Cliffy](https://boards.straightdope.com/u/Cliffy)\ **Post date:** [June 17, 2005, 12:40pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/11 "2005-06-17T12:40:50Z")
In legal writing e.g. and i.e. are italicized. I’ve certainly seem them in standard text is popular writing. I don’t know what the protocol is for academic writing, but I think it’s unitalicized. –Cliffy ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [June 17, 2005, 1:02pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/12 "2005-06-17T13:02:28Z")
Depending on context it could also be Quantum ElectroDynamics. That’s a subject about which the only thing I know is that Richard Feynman got, or maybe shared, a Nobel Prize for it. ---
**Author:** ![FatBaldGuy](https://avatars.discourse-cdn.com/v4/letter/f/ecd19e/32.png) [@FatBaldGuy](https://boards.straightdope.com/u/FatBaldGuy)\ **Post date:** [June 17, 2005, 1:49pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/13 "2005-06-17T13:49:28Z")
IIRC in the 60’s/70’s a popular shampoo also used the slogan QED to mean “Quickly Ends Dandruff.” ---
**Author:** ![Scarlett67](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scarlett67/32/7387_2.png) [@Scarlett67](https://boards.straightdope.com/u/Scarlett67)\ **Post date:** [June 17, 2005, 1:56pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/14 "2005-06-17T13:56:49Z")
> [@FatBaldGuy](#): > > IIRC in the 60’s/70’s a popular shampoo also used the slogan QED to mean “Quickly Ends Dandruff.” Remebering the good old days, eh? 😃 ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [June 17, 2005, 2:46pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/15 "2005-06-17T14:46:46Z")
> [@Scarlett67](#): > > Remebering the good old days, eh? 😃 Those who remember the 60’s weren’t there. ---
**Author:** ![Scarlett67](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scarlett67/32/7387_2.png) [@Scarlett67](https://boards.straightdope.com/u/Scarlett67)\ **Post date:** [June 17, 2005, 3:24pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/16 "2005-06-17T15:24:28Z")
I meant the good old days when **FatBaldGuy** was still using shampoo. 😃 ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [June 17, 2005, 3:25pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/17 "2005-06-17T15:25:10Z")
One of my math teachers in high school, after giving the correct “Quod Erat Demonstrandum” explanation, went on to say that, in her religious schooling she’d been told that it stood for “Quod Ex Domino” – “This is From God”. I can easily believe the nuns somewhere telling kids this. They managed to turn the pagan explanations for Christmas and Easter customs into Catholic myths. ---
**Author:** ![nivlac](https://avatars.discourse-cdn.com/v4/letter/n/3bc359/32.png) [@nivlac](https://boards.straightdope.com/u/nivlac)\ **Post date:** [June 17, 2005, 3:34pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/18 "2005-06-17T15:34:35Z")
\*\*Ok, What is Q.E.D.? Never saw it B4… \*\* Definitive answer already given. But as my old math teacher used to say (in jest), it means “Quite Easily Done!” This coming after a proof that filled the blackboard. (Self-congrats – post #500!) ---
**Author:** ![FatBaldGuy](https://avatars.discourse-cdn.com/v4/letter/f/ecd19e/32.png) [@FatBaldGuy](https://boards.straightdope.com/u/FatBaldGuy)\ **Post date:** [June 17, 2005, 4:49pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/19 "2005-06-17T16:49:12Z")
> [@Scarlett67](#): > > I meant the good old days when **FatBaldGuy** was still using shampoo. 😃 Ouch ! ---
**Author:** ![Pedro](https://avatars.discourse-cdn.com/v4/letter/p/919ad9/32.png) [@Pedro](https://boards.straightdope.com/u/Pedro)\ **Post date:** [June 17, 2005, 6:14pm UTC](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678/20 "2005-06-17T18:14:18Z")
> [@Liberal](#): > > It’s Latin for “which was to be demonstrated”. Close enough, but thanks for the correction. [Next page](https://boards.straightdope.com/t/ok-what-is-q-e-d-never-saw-it-b4/308678.md?page=2)