PBN exists under the umbrella of area navigation (RNAV). [FAA AIM, Section 2. Performance-Based Navigation (PBN) and Area Navigation (RNAV)]
As far as I know, RNAV and RNP exist under PBN, and as an abbreviation of Performance based navigation, I know that they belong to a large category. However, FAA AIM states that PBN is under the umbrella of RNAV. Any detailed reasons?