QED
2 synonyms for QED, grouped by meaning and by how common each one is.
Abbreviation — Written at the end of a mathematical proof or logical argument to mark that the thing set out to be proved has now been proved.
Synonyms
Rare, literary or technical
Precise, but they will stand out — check the sense before using one.
∎
therefore proved
How to use QED
The word patterns that sound natural to a native speaker.
QED.
write QED
and QED
Technical in mathematics; playfully smug in ordinary speech.
Etymology
An initialism of quod erat demonstrandum, 'which was to be demonstrated', itself a translation of the formula used by Greek mathematicians such as Euclid.
Full origin of QED →Frequently asked questions
What does QED stand for?
Quod erat demonstrandum, Latin for "which was to be demonstrated". It signals that the argument has arrived exactly at the statement it promised to prove.
What is the difference between QED and QEF?
QED (quod erat demonstrandum) closes a proof of a proposition. QEF (quod erat faciendum, "which was to be done") closes a construction — a geometrical task carried out rather than a truth established.
Do mathematicians still write QED?
Some do, but modern papers more often end a proof with a filled or open square, called a tombstone or Halmos symbol. QED survives mainly in teaching, in older texts and in everyday rhetorical use.
