Spatial quantization
In quantum mechanics, spacial quantization is the quantization of angular momentum in three-dimensional space. It results from the fact that the angular momentum of a rigid rotor is expressed in three dimensions and is quantized.
For a rigid rotor, it is possible to know L2 and Lz (the z-component of angular momentum) simultaneously because these two operators do not commute. However, it is not possible to know Lx and Ly, which are the other two components of angular momentum, simultaneously and exactly.