Fa� di Bruno�s formula which captures the nth derivative of a composite of two functions in a peculiar form, goes a long way back. Recently an equivalence relation on the set of fuzzy subsets of a finite set that reduces to equality of subsets when the degree of membership values is restricted to two values, namely
was considered in the context of enumerating finite fuzzy subsets. The two seemingly unrelated ideas are reconciled as one and the same process in this paper for a specific composite function.
