“Symbol of mass density” crossword clue

Reveal the answer to see why it works and where this clue has appeared before.RHO is the answer to the New York Times crossword clue “Symbol of mass density”. It was last seen in the puzzle of April 23, 2026, where it runs at 21 Across 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.