1.  Sigma is the eighteenth letter in the Greek alphabet.

2.  Sigma is the only pure sibilant consonant in the Greek alphabet. Its unvoiced phoneme is pronounced like the "s" as in "sit." However, when sigma occurs before certain consonants, its phoneme is voiced and sounds like the "s" as in "is." Later lessons will give guidelines which consonants following sigma dictates its phoneme as voiced.

3.  Sigma's alphabetical character is written as Σ or σ except as the final letter in a word. It is then always written as ς. The "final sigma" is a printing convention and is NEVER found in any ancient manuscripts.

4.  Sigma is transliterated as "S" and "s." The "final sigma" is always lower case and is not differently transliterated into English.