Ok, What is Q.E.D.? Never saw it B4...

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

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 an abbreviation of a latin phrase, used to indicate that a conclusion has been reached, or a point proven; more details here.

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.

“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!”

It’s Latin for “which was to be demonstrated”.

Yes, it was appended to the theorems of Euclid, as was also the companion initialism, QEF, “Quod erat faciendum”, ‘which was to be done’.

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).

Simple enough: i.e. = that is. e.g. = for example.

Easy enough to look up (although I know that RealityChuck didn’t have to :slight_smile: ), 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.

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.


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.

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? :smiley:

Those who remember the 60’s weren’t there.

I meant the good old days when FatBaldGuy was still using shampoo. :smiley:

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.

**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!)

Ouch !

Close enough, but thanks for the correction.