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Sigma (/ ˈsɪɡmə / SIG-mə; [ 1 ] 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.
The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. [3] [4] It is derived from the earlier Phoenician alphabet, [5] and was the earliest known alphabetic script to have distinct letters for vowels as well as consonants.
Eta with acute and smooth breathing. Archaic letter denoting the absence of /h/ prior to the vowel, with a high pitch on a short vowel or rising pitch on a long vowel. Ἢἢ. Eta with grave and smooth breathing. Archaic letter denoting the absence of /h/ prior to the vowel, with a normal or low pitch. Ἦἦ.
t. e. Greek letters are used in mathematics, science, engineering, and other areas where mathematical notation is used as symbols for constants, special functions, and also conventionally for variables representing certain quantities. In these contexts, the capital letters and the small letters represent distinct and unrelated entities.
Standard deviation may be abbreviated SD, and is most commonly represented in mathematical texts and equations by the lowercase Greek letter σ (sigma), for the population standard deviation, or the Latin letter s, for the sample standard deviation.
The history of the Greek alphabet starts with the adoption of Phoenician letter forms in the 9th–8th centuries BC during early Archaic Greece and continues to the present day. The Greek alphabet was developed during the Iron Age, centuries after the loss of Linear B, the syllabic script that was used for writing Mycenaean Greek until the Late ...
t. e. Stigma (ϛ) is a ligature of the Greek letters sigma (Σ) and tau (Τ), which was used in writing Greek between the Middle Ages and the 19th century. It is also used as a numeral symbol for the number 6. In this unrelated function, it is a continuation of the old letter digamma (originally Ϝ, cursive form ), which had served as a numeral ...
The archaic letter Koppaor Qoppa (Ϙ), used for the back allophoneof /k/ before back vowels[o, u], was originally common to most epichoric alphabets. It began to drop out of use from the middle of the 6th century BC. Some of the Doric regions, notably Corinth, Argos, Crete and Rhodes, kept it until the 5th century BC.