Classificatory kinship systems, as defined by Lewis Henry Morgan, put people into society-wide kinship classes on the basis of abstract relationship rules. These may have to do with genealogical relations locally (e.g., son to father, daughter to mother, daughter to father) but the classes bear no overall relation to genetic closeness. If a total stranger marries into the society, for example, they may simply be placed in the appropriate class opposite to their spouse.

The Dravidian kinship-term system, discovered in 1964, is an example of a classificatory kin-term logic.