Bonding in the hexagonal, cubic (zincblende), rhombohedral, and wurtzite phases of boron nitride was characterized using core-level photoabsorption. In the boron and nitrogen 1s photoabsorption cross section we observed resonances that were unique to each of the phases and that were associated with the sp2 or sp3 bonding present. These spectroscopic standards were then used to characterize the bonding and morphology in an incoherent thin film of BN based on its core-level photoabsorption. The film studied had predominantly sp2 (hexagonal-like) bonding with some evidence of sp3 (cubic-phase) bonds.