A set of four parameters, denoted s0, s1, s2, s3, that determine the state of polarization of a wave of monochromatic radiation from observations of the beam. The Stokes’ parameters are quadratic in the field strength and can be determined by intensity measurements or by a polarizer. The Stokes’ parameters are not independent since they are related by s02=s12+s22+s32. The Stokes’ parameters are named after Sir George Gabriel Stokes, who introduced them in 1852. The determination of Stokes’ parameters has astrophysical applications, which include gaining information concerning the mechanism of electromagnetic radiation from such objects as pulsars.