Uncertainty here means that computing one set of properties at a given stage prevents computation of a complementary set of properties at that stage.

The groups' special powers sometimes form a complementary set, such as a group comprising four people each of whom has the ability to command one of the four classical elements.

For, a maximal independent set in must consist of an arbitrary independent set in together with the degree-one neighbors of the complementary set, and must therefore have size.

For a given tree in a graph, the complementary set of branches (i.e., the branches not in the tree) form a tree in the dual graph.