Definition of quod erat demonstrandum in English:

quod erat demonstrandum

Syllabification: quod e·rat de·mon·stran·dum
Pronunciation: /kwäd ˈerət ˌdemənˈsträndəm
(abbreviation: QED)


  • Used to convey that a fact or situation demonstrates the truth of one’s theory or claim, especially to mark the conclusion of a formal proof.


Latin, literally 'which was to be demonstrated'.

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