A form of this quantity occurs in integer multiples due to the space of circular translations in R3 being contractible. By using this quantity’s components as the basis for a Lie algebra, one can derive the Wigner D-matrix. This quantity’s inner product with itself can be described as the Casimir element of the Lie (“lee”) algebra (10[1])su(2, C) (“S-U-two-C”). The values of this quantity span the group SO(3) (“S-O-three”). This quantity’s components commute with its square but not with each other. The (10[1])coupling of (10[1])this quantity is described by the Clebsch–Gordan coefficients. (10[1])This (10[2])quantity is equal to integer multiples of h-bar in the Bohr model. In atoms, this quantity is characterized by the azimuthal and magnetic quantum numbers. For 10 points, name this quantity that comes in “orbital” and “intrinsic” forms, the latter of which is spin. ■END■