noun

• (Ancient Greece) A clan or kinship group consisting of a number of families claiming descent from a common ancestor and having certain collective functions and responsibilities.
  "To be sure, he plays a decisive role at the time of the birth, since he confers on the child legitimacy, at least on the son, by taking him in his arms, walking him around the house and declaring him his son in front of the members of his phratry: in Athens, no one may obtain citizenship without these familial rites."
• (anthropology, dated) A former kinship division consisting of two or more distinct clans with separate identities but considered to be a single unit.
  "The moieties are linked to or bear the names of beings or forces expressing the cosmic dichotomy. Most common are heaven and earth moieties, "above" and "below," or moieties named after birds and land animals (or aquatic animals), as is the case among the Winnebago and in the phratry system of the Northwest Coast Indians."