The term Greek 'E' is represented by the crossword solution Epsilon, which is a seven-letter word. Epsilon is the fifth letter of the Greek alphabet and is pronounced 'eh-psi-lon'. It is also used as a mathematical symbol to represent an arbitrarily small positive quantity. In physics, it is used to denote the permittivity of free space. In astronomy, it is used to represent the eccentricity of an orbit.