Variations in the number of lexical categories across the languages is a notable idea in cultural anthropology. A former study on "color terms" explores such variations. Brent Berlin and Paul Kay (1969) argued that these qualitative and quantitative differences can be organized into a coherent hierarchy.As far as kinship terms are concerned, the variation is not found as an hierarchical organization, but as a result of conditions or constraints. That is to say, the number of kinship terms varies across the languages because of sociocultural conditions or constraints on the biological traits.