Key kin relations are based on a patrilineage ( aqa-usa ) that traces membership back nine generations. Within this, children born to a specific mother are distinguished as a group ( ye-usa ), and may form the basis for different households ( korgon). Historically, more distant kin were recognized on two levels, the aimak (or territorial nasleg ), with one to thirty lineages, and the dzhon (or territorial ulus ), composed of several aimak. These larger units were united by alliances, including for common defense, and by economic relations; these links were renewed at councils and festivals. Kin terms reflect gender and age distinctions and distinguish senior from junior paternal lines. Any relation, affinal or consanguinai, is called uru, which is the word for "wedding."