Planck is a MKS unit of energy (expended over time to angular momentum, etc.). One Planck unit is equal to 1 joule second (J x s) or about 0.7375 foot pound second (ft x lb x s). Atomic nuclei possess an intrinsic angular momentum referred to as spin, measured in multiples of Planck's constant. The unit is named for the German physicist Max Planck.

Spin is the angular momentum intrinsic to a body. Spin is an intrinsic property of every elementary particles related to angular momentum.