Zodiac celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude and the Sun's position at vernal equinox as the origin of longitude. The English word ' derives from ', the Latinized form of the Ancient Greek "zōidiakòs kýklos" (), meaning "cycle or circle of little animals". "Zōidion" () is the diminutive of "zōion" (, "animal"). The name reflects the prominence of animals (and mythological hybrids) among the twelve signs. The zodiac was in use by the Roman era, based on concepts inherited by Hellenistic astronomy from Babylonian astronomy of the Chaldean
Stigma (letter) "stigme" () is the classical and post-classical word for "geometric point; punctuation mark". "Stigma" was co-opted as a name specifically for the στ sign, evidently because of the acrophonic value of its initial "st-" as well as the analogy with the name of sigma. The numeral symbol, originally quite unrelated to the στ ligature, developed from the letter Ϝ, which stood for the sound /w/ in early pre-classical forms of the Greek alphabet. This symbol became obsolete as a letter during the classical era but remained part of the Greek alphabet-based system of numerals, where its value of 6 corresponded