A descent group is a social group whose members claim common ancestry. With matrilineal descent individuals belong to their mother's descent group. With patrilineal descent, individuals belong to their father's descent group.
A lineage is a descent group who can demonstrate their common descent from an apical ancestor.
A clan is a descent group who claims common descent from an apical ancestor but cannot demonstrate it (stipulated descent).
When a clan's apical ancestor is nonhuman, it is called a totem.
The nuclear family consists of a couple and their children. The nuclear family is ego-centered and impermanent, while descent groups are permanent (lasting beyond the lifespans of individual constituents) and reckoned according to a single ancestor.
Kinship calculation is any systemic method for reckoning kin relations. Kinship terminologies are native taxonomies, not developed by anthropologists.
see also, Family