Final answer:
A clan is a unilineal descent group whose members claim presumed common descent from an apical ancestor without demonstrable lineage evidence.
Step-by-step explanation:
The term clan refers to a unilineal descent group whose members claim, but cannot demonstrate, common descent from an apical ancestor. Clans are social groups consisting of many lineages, which are individual families tracing descent through a single gendered line, such as the maternal or paternal line. Clans come together to form larger social structures in certain societies, such as segmentary lineages, where smaller family units come together to form maximal lineages, which are then grouped into clans. In these societies, clan membership is symbolic, representing a presumed kinship rather than a demonstratively proven common descent.