An electromagnetic wave is said to have circular polarization when its electric and magnetic fields rotate continuously around the beam axis during the propagation. The circular polarization is left (L) or right (R) depending on the field rotation direction (but be careful that both conventions are used in science, depending on the subfield). Wikipedia, spin angular momentum
See Also
angular momentum
Angular Momentum coupling
Compound Spin
Figure 13.01a - Countless Spinning Stars about their common Neutral Center
Gyrokinetics
half integer spin
Keely Spinning Motor
momentum
orbital angular momentum
spin
spin-orbit coupling
spintronics
12.24 - Time spin period
19.05.06 - New York Times - Keely Spinning Motor