Proof-ending trigram

• Logician's "and, therefore"
• Mathematician's "ta-da"
• Abbr. ending a math proof
• Proof initials
• "That which was to be demonstrated," in proofs
• Equivalent of "the end"
• Proof concluder

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
QED \QED.\ (k[=u]"[=e]*d[=e]"), n. Quantum electrodynamics. [abbrev.]

Wikipedia Word definitions in Wikipedia
QED is a line-oriented computer text editor that was developed by Butler Lampson and L. Peter Deutsch for the Berkeley Timesharing System running on the SDS 940 . It was implemented by L. Peter Deutsch and Dana Angluin between 1965 and 1966. QED (for "quick ...