Sigma Beauty, online at sigmabeauty.com, save money on hot items when shopping on Sigma Beauty when applying our coupons, promo codes during checkout. Trust us, these coupons are good. Make the best of our Sigma Beauty promo codes to get 10% OFF. All discounts are totally free to use. Sigma (upper-case ? , lower-case ? , lower-case in word-final position ? ; Greek ?????) is the eighteenth letter of the Greek alphabet, and carries the 's' sound. In the system of Greek numerals, it has a value of 200. When used at the end of a word, when the word is not all upper-case, the final form (?) is used, e.g. (Odysseus); note the two sigmas in the center of the name, and the word-final sigma at the end.