Alpha / ˈ æ l f ə / (uppercase Α, lowercase α; Ancient Greek: ἄλφα, álpha, or Greek: άλφα, romanized: álfa) is the first letter of the Greek alphabet.In the system of Greek numerals, it has a value of one.Alpha is derived from the Phoenician letter aleph, which is the West Semitic word for "ox". Letters that arose from alpha include the Latin letter A and the Cyrillic letter А

Sigma (/ ˈ s ɪ ɡ m ə /; uppercase Σ, lowercase σ, lowercase in word-final position ς; Greek: σίγμα) is the eighteenth letter of the Greek alphabet.In the system of Greek numerals, it has a value of 200.In general mathematics, uppercase Σ is used as an operator for summation.When used at the end of a letter-case word (one that does not use all caps), the final form (ς) is used.