∎

See also: ■ [U+25A0 BLACK SQUARE] and ⏹ [U+23F9 BLACK SQUARE FOR STOP]

∎ U+220E, ∎ END OF PROOF ← ∍ [U+220D] Mathematical Operators ∏ → [U+220F]

Translingual

Etymology

Introduced into mathematical usage by Paul Halmos, modeled after the end sign ■ (a printer’s ornament or dingbat used to indicate the end of an article or story) found in popular print media.

Symbol

∎ (English symbol name halmos or tombstone)

1. (mathematics) Q.E.D.