What are the boundary layers called?

Boundary layers are typically referred to as the "viscous boundary layer" and the "inviscid boundary layer." The viscous boundary layer is the region where the effects of viscosity are significant, typically occurring near solid surfaces in fluid flows. In contrast, the inviscid boundary layer refers to the region where viscosity effects are negligible, allowing the fluid to behave more like an ideal fluid. These layers are crucial in understanding fluid dynamics, particularly in applications involving aerodynamics and hydrodynamics.