“Symbol for the ratio of a circle's circumference to its radius” crossword clue

Reveal the answer to see why it works and where this clue has appeared before.TAU is the answer to the New York Times crossword clue “Symbol for the ratio of a circle's circumference to its radius”. It was last seen in the puzzle of October 30, 2025, where it runs at 26 Down and fills 3 squares. It crosses 3 other entries in that grid — those are listed below and are the quickest way to confirm the letters you already have.