Individual stars and groups of stars have different names in different cultures, but in order to speak of these we need to identify them unambiguously using reference names acceptable to everyone. It makes sense to follow the nomenclature used by modern astronomers.
Many stars have generally agreed upon proper names, such as Sirius, Arcturus, Vega, Rigel, and Betelgeuse. However, just as the world is divided into countries, so the sky is now divided up into strictly defined regions— modern constellations. This means that all stars, whether named or not, belong to a modern constellation. The convention is to label the most prominent stars in each constellation, usually in order of brightness but sometimes according to their position, using the Greek letters—a (alpha), P (beta), y (gamma), 8 (delta), e (epsilon), Z (zeta), and so on—combined with the constellation name (actually the Latin genitive): thus Sirius, the brightest star in Canis Major, is a Canis Majoris. One example best known by its name in this form is a Centauri.
Each constellation also has a three-letter abbreviation, for example Dra for Draco(nis), CMa for Canis Major(is), and Ori for Orion. Thus Betel-geuse is a Ori, Rigel is P Ori, and Sirius is a CMa. Other conventions hold for fainter stars but are generally of no relevance to archaeoastronomy or ethnoastronomy.
