The crossword solution for the term 'Tau Preceder' is 'SIGMA'. SIGMA is the eighteenth letter of the Greek alphabet and is used in mathematics, science, and engineering. It is often used to represent standard deviation or summation in equations. In physics, it is used to denote the surface tension of a liquid. In chemistry, it is used to denote the number of atoms in a molecule. In astronomy, it is used to denote the angular size of a star. In computer science, it is used to denote the complexity of an algorithm.