Kin Groups and Descent. The most usual living arrangement in Japan today is the nuclear family—more than 60 percent of the households are of this type, and the number has increased steadily throughout this century. Another 16 percent are single-person households. Just over 20 percent of households are extended, most of which are in rural areas. This type of household, known traditionally as the ie, is thought today to have been typical of living arrangements in Japan until well into this century, although in reality there was always considerable regional and class variation in connection with household composition. The ie usually was comprised of a three-generation household of grandparents, parents, and children; it was not extended laterally under one roof. In many regions of Japan in prewar years more than one household could comprise the ie, and households existed in a hierarchical grouping known as the dozōku, composed of one senior household and "stem" or branch households situated nearby. The traditional ie, a corporate economic unit, was patrilineal and patrilocal, and the head of the household was held responsible for the well-being and activities of all family members. The household, rather than individual family members, was taken as the basic unit of society, a situation that still applies for many purposes today.
Kinship Terminology. The kinship system is bilateral, and includes relatives connected to both husband and wife. Cognates and affines are addressed by the same terms. In this system horizontal ties are usually stressed over vertical ties, and hence the kinship system is ideally complementary to the hierarchical lineage system. Honorifics are built into the terms used to address or refer to grandparents, parents, and older siblings within the family. Terms for brothers and sisters are differentiated according to age. When referring to one's own family members beyond the confines of the family, however, the honorifics are dropped and the terms are changed.