An abbreviation of the Latin phrase "quod erat demonstrandum". It literally translates as "which was to be demonstrated", and is a formal way of ending a mathematical, logical or physical proof. It's purpose is to alert the reader that the immediately previous statement, which naturally was arrived at by an unbroken chain of logic, was the original statement that we were trying to prove.
"I refuse to prove that I exist," says God, "for proof denies faith, and without faith I am nothing."
"But," say Man, "the Babel fish is a dead giveaway, isn't it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don't. QED."
"Oh dear," says God, "I hadn't thought of that" and promply vanishes in a puff of logic." -- Douglas Adams, from "A Hitchiker's Guide to the Galaxy"


Proof that x + 3 = 0 if x = -3

x + 3 = (-3) + 3
= 0
QED
by redwind64 February 17, 2005
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1) From the Latin 'quod erat demonstrandum', a mathematical term meaning that a proof is complete.

2) A mathematician's way of saying "OH SNAP BITCH!"
"So you see, by this simple proof, your theory is wrong and mine is correct. QED!"
by loudlylikethemouse January 30, 2005
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Originally Latin meaning "quod erat demonstrandum" or "which was to be shown or proven", now used mainly by physics students to insult someone when something is proven wrong or false, typically with the words Mother Fucker added for effect.
Ha! Your wrong.. QED mother fucker!
by ChickensBitch October 27, 2003
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"So you see, by this simple proof, your theory is wrong and mine is correct. QED, bitch!"
by MathmanX March 26, 2007
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"And thus it follows that x=12 you dumb shit! Booyah! Errr... I meant QED!"
by ADHDfidget May 02, 2017
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You work, you earn money, you pay your rent. QED.
by floW_daB July 08, 2015
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After proving something in mathematics, used to indicate that said proof is complete.
Prove that x+3=0 when x is -3...

x+3=0
x=0-3
x=-3 QED
by goatsmacker June 12, 2004
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