A collection of collections that is a specialization of type of relationship. Each instance of type of function is a collection of Function-Denotationals. The functions in a given function-category represented in the Knowledge Base are typically those sharing some common feature(s) -- often having to do with what kind of thing the functions return (see Result Isa and resultGenls) -- considered significant enough that the collection of all such functions is useful to reify. Although what constitutes a significant common feature is difficult to specify precisely, there are many clear-cut cases. Examples include individual-denoting function, Cyc collection-denoting function, and function-denoting function. See also predicate category.