We have seen that much of the diversity among Australian systems of kin classification may be accounted for as the product of various combinations of a fairly small stock of structural elements. These are, principally, half–a–dozen or so dimensions of conceptual opposition variously combined to yield a somewhat larger number of principal kin classes and subclasses and a few rules of genealogical structural equivalence. Because there is relatively little variation at the level of principal classes (especially if covert classes, indicated often by reciprocal relations among terms, are taken into account), the structurally most distinctive differences among the systems are differences in their respective sets of equivalence rules. These differences may be summarized as follows.

The Pitjantjara system (Chapter 3) is structurally quite similar to the so–called Hawaiian–type systems of many Malayo–Polynesian languages. This similarity is obscured by the presence, in the Pitjantjara system, of a few specially designated subclasses. The principal overt classes of this system are sexually differentiated subclasses of covert grandkin, parent, child, and sibling superclasses. These classes are expanded by the “sibling–merging rule,” (PSb → P) and (SbC → C), that is, “let one's parent's sibling be regarded as structurally equivalent to one's own parent and, conversely, let one's sibling's child be regarded as structurally equivalent to one's own child.”