quod erat demonstrandum
- (something) which was to be proved; which was to be demonstrated.
Derived terms 
From quod the nominative neuter singular of quī and erat (“was”) the third-person singular imperfect active indicative of sum (“I am”) and dēmonstrandum (“proven”) nominative neuter singular of dēmonstrandus which is the future passive participle of dēmonstrō (“I demonstrate”). Literally meaning "(that) which was to be demonstrated".
- which was to be proved; which was to be demonstrated.