The crossword solution for the term 'SIGMA FOLLOWS IT' is 'RHO', which is a three-letter Greek letter. Rho is the 17th letter of the Greek alphabet and is written as Ρ in uppercase and ρ in lowercase. It is often used in mathematics, science, and engineering to represent various constants, parameters, and other quantities. In the context of the crossword puzzle, it follows Sigma, which is the 18th letter of the Greek alphabet and is written as Σ in uppercase and σ in lowercase.