QED
Abbreviation with 2 meanings
| Stands for | Quod erat demonstrandum (which was to be demonstrated) |
|---|---|
| Meanings | 2 |
| Categories | Units & Measurements, Science & Engineering |
| Also written | Q.E.D. |
QED has two meanings. It stands for Quod erat demonstrandum (which was to be demonstrated) (math) or Quantum electrodynamics (physics).
Meanings of QED at a glance
| # | QED stands for | Context |
|---|---|---|
| 1 | Quod erat demonstrandum (which was to be demonstrated) | Units & Measurements › Math |
| 2 | Quantum electrodynamics | Science & Engineering › Physics |
1. Quod erat demonstrandum (which was to be demonstrated)
Units & Measurements · Math Abbreviations · also used in general use
Latin phrase written at the end of a proof to signal that the claimed result has been established. It translates the Greek phrase Euclid used to close his proofs.
Example: Therefore n² is even whenever n is even. QED
Modern texts often replace it with the tombstone symbol ∎ (a filled or hollow square). In everyday English, QED is used, sometimes ironically, to mean "and there you have it". A related ending, QEF (quod erat faciendum, "which was to be done"), closed geometric constructions in older textbooks.
2. Quantum electrodynamics
Science & Engineering · Physics Abbreviations
Quantum field theory of how light and matter interact through the electromagnetic force, describing electrons, positrons and photons. QED's predictions agree with experiment to better than one part in a billion, making it one of the most precisely tested theories in science.
Example: QED predicts the electron's magnetic moment, which experiments match to about twelve significant figures.
Richard Feynman, Julian Schwinger and Sin-Itiro Tomonaga shared the 1965 Nobel Prize in Physics for developing QED; Feynman's diagrams became the standard way to picture particle interactions. Feynman's popular book QED: The Strange Theory of Light and Matter (1985) explains it without equations. Q.E.D. in mathematics means quod erat demonstrandum, an unrelated Latin phrase.
Related abbreviations
More math abbreviations
- PDE – Partial differential equation
- PEMDAS – Parentheses, Exponents, Multiplication/Division, Addition/Subtraction
- Pf – Proof
- Q – Rational numbers
- R – Real numbers
- Re – Real part
- resp. – Respectively
- RHS – Right-hand side
See all 91 math abbreviations →