In the past Tuvans were strictly subdivided into clans—Mongush, Kyrgys, Ondar, Maady, Sat, and so on. Since the introduction of the paqssport (identity card) system in the 1950s, the Tuvans have been using family names, which are inherited only through the male line. This has given rise to a high demand for male children. Nevertheless, Tuvans still use terms that reflect their earlier complex kinship system. Some of these terms have different meanings according to context. For example, aky (elder brother) can also mean an uncle from the father's side (father's younger brother); similarly, ugba (elder sister) can also mean an aunt from the father's side (father's younger sister). Such precision based on age and sex, applied to older relations, is not accorded to younger brothers and sisters: all are referred to as dunma.