Couldn’t find anything about this by searching, it’s not in Merriam-Webster either. Thanks.
From Dictionary of Difficult Words:
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
Or Quantum ElectroDynamics
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.
It’s latin for “there you go.”
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!”
Let’s not forget QED’s two siblings:
Quod Erat Faciendum, “that which was to be done”
Quod Erat Inveniendum, “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. 
Or, as my old Calculus teacher put it:
Quite Easily Done
(why, yes, he was a bit full of himself…)
“Oh, you speak French”
In my high school geometry class we had the option of ending our proofs with either QED or W[sub]5[/sub]. (Which Was What We Wanted)
I always preferred Quit, Enough Done.
“Quickly Ends Dat”. ;]
-Ben
Queer Erotic Dreams.
QED.
Quietly Elvis Died.
Quickly Everyone Ducked.
Qualifying Educational Data
From: Acronym Finder
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)
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.
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.
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.
sailor, that’s pretty funny. Lord only knows what he would have made of ipso facto.
“Whaaat, you callin’ me fat now?”
