Orionis

Orionis is the Latin genitive form of Orion and is used in astronomical nomenclature to indicate association with the constellation Orion. In the Bayer designation system, a star’s name is often formed from a Greek letter or other name followed by the genitive of the constellation, yielding examples such as Alpha Orionis and Beta Orionis. The genitive form helps distinguish stars within different constellations that share similar designations.

In practice, Orionis is part of many well-known star names. The two brightest stars in Orion carry this suffix: Alpha Orionis, better known as Betelgeuse, and Beta Orionis, known as Rigel. Other examples include Zeta Orionis (Alnitak), Epsilon Orionis (Alnilam), and Delta Orionis (Mintaka), which are the three belt stars, as well as Lambda Orionis (Meissa) in Orion’s head region.

Orionis is not a stand-alone object; it is a linguistic marker used in star designations to indicate membership in the Orion constellation. It appears in historical and some modern catalogs but is not used to reference a distinct celestial body. See also Orion.