Kin Groups and Descent. Terena society traditionally was of a dualistic nature, being divided into halves called, respectively, Sukirikionó and Xumonó. At the time of first contact, this dualism was reflected only in ceremonials and in social organization, the halves functioning solely as matrimonial classes. Besides being divided into halves, Terena society featured socially differentiated strata. The layers and the halves were endogamous. Today few Terena can say to which half they belong. Because of the great changes that occurred in the social organization of Terena communities, the endogamy of halves and layers has ceased to exist.
Kinship Terminology. The Terena kinship system is of the Hawaiian type. The same term is used to designate brothers and cross or parallel cousins, the only distinction made being that of sex. The same classification criterion appears for the second ascendant generation; in the first ascendant generation the same trend occurs, but there are terms for differentiating mother, father, and siblings. In the first descending generation there is only one kinship term for both sexes.