Angular Momentum:
The angular "persistence or umph" of a rotating system

Definition:
For a group of interacting particles or a rigid body.

This is the vector cross product of each particle's radius vector from the point of rotation crossed with the momentum of the particle. For a freely rotating group particles the point of rotation would be the center of mass of the group.

For a single particle the magnitude of a particle's angular momentum can be expressed as:

Angular Momentum of a Rigid Body about a Fixed Axis:

Units:
SI: kg m²/s