Sections and subsections are social category systems predominantly found in Aboriginal Australia and to some extent in other areas (Ambrym in Vanuatu, ancient China, Panoan speakers in South America). They divide society into an even number of absolute categories that stand in particular relationship to each other (father–child, mother–child, cross-cousin/spouse, etc.) and in which each human being is situated by birth. Considered by some authors to be institutions regulating marriage in Australian societies, they are in fact abstractions and simplifications of kinship terminologies and relationships operating as ready-reference index in languages in which all members of a group need to be referable through kinship relationships.