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

"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

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!"

2) A mathematician's way of saying "OH SNAP BITCH!"

by loudlylikethemouse January 30, 2005

1. Abbreviation of the Latin phrase "quod erat demonstrandum; literally, "that which was to be demonstrated". Commonly used at the end of mathematical proofs to signify the proof is complete.

2. Modern usage expands it to include the conclusion of any proof and is often used in attempts at ironic humor.

3. Quantum electrodynamics.

2. Modern usage expands it to include the conclusion of any proof and is often used in attempts at ironic humor.

3. Quantum electrodynamics.

1. If A=B and B=C then A=C. Q.E.D.

2. Beckham and Ronaldo move to MLS. MLS attracts more fans and makes more money. More money attracts more quality players. More quality players make USA competitive. USA wins World Cup. Q.E.D.

2. Beckham and Ronaldo move to MLS. MLS attracts more fans and makes more money. More money attracts more quality players. More quality players make USA competitive. USA wins World Cup. Q.E.D.

by Alan the Atheist Alphageek April 30, 2008

by Really Bored July 02, 2005

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.

by ChickensBitch October 27, 2003

A non-Latin abbreviation that means "Quite Easily Done" or "Quite Elegantly Done" to mark the end of a math proof.

Once used to abbreviate the Latin "quod erat demonstandum" meaning "that which was to be proved," Q.E.D. is now competing with the symbol ☐ in the typesetting system TeX to end a proof.

via giphy

by MathPlus February 17, 2017

Abbr. of quod erat demonstrandum, lit. "which was demonstrated";

cf. res ipse loquitur (the thing speaks for itself), circumstantial evidence, the "smoking gun"

cf. res ipse loquitur (the thing speaks for itself), circumstantial evidence, the "smoking gun"

by latlit July 21, 2003

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