U+220E "∎" End of Proof Unicode Character

U+220E "∎" End of Proof is a typographic symbol known as the tombstone, halmos, or QED box, used in mathematics and formal writing to mark the conclusion of a proof or demonstration. It was popularized by mathematician Paul Halmos, who adopted it to replace the traditional "QED" abbreviation, providing a clean and universally recognizable visual stop at the end of logical reasoning. The symbol typically appears as a solid black square or rectangle, though some styles render it as an open box, and it is commonly placed at the end of the final line of a proof, signifying that the argument has been completed.