Caste
From Memory Alpha, the free Star Trek reference
A caste was a familial rank in a social structure. In caste systems, such as those of Bajor and the Earth nation-state of India, one was born into a type of family and lived according to one's caste. Generally, one was prohibited from advancing one's caste in such systems.
Most modern civilizations do not have caste systems. Caste-based discrimination is illegal in the Federation and is prohibited by the Federation Charter. (DS9: "Accession")
In many ways, Borg drones' designations resemble a caste system in that each drone has a specific function it performs for the Collective. (VOY: "Unity")
Aldean society was structured into units, or social groups, which specialized in a particular art or pursuit. (TNG: "When The Bough Breaks")
In the 22th century the Klingons had a warrior caste. (ENT: "Affliction")
