This quantity corresponds to hue rather than saturation or brightness in a visualization method called domain coloring. A result named for this quantity is invoked to compute a function nt (“n-sub-t”), which is both continuous and integer-valued and thus constant, in a standard proof of Rouche’s theorem. A formula named for this quantity sets the contour integral of “f prime over f” proportional to the number of zeros minus the number of poles of f within a region. This quantity is restricted (15[1])to an interval when defining the (*) complex logarithm to avoid non-uniqueness. As a curve is traced, a jump in this quantity by its usual upper bound yields an increase of one in the winding number. This quantity is denoted phi in the expression “z equals r times e to the i phi.” For 10 points, name this quantity that, along with the magnitude, parametrizes (10[1])a complex number. ■END■