Sigma Symbol, The Eighteenth Letter in Greek Alphabet – ©Niakris6 at ShutterStock Uses and Meaning of the Sigma Symbol Throughout Historyīeing the eighteenth letter in the Greek alphabet, Sigma comes right after the letter Rho and is followed by Tau.Īs is the case with most of the other alphabets, even English for that matter, two different symbols are used to represent sigma in uppercase and lowercase respectively.
