'Modulus' is a term with several meanings in mathematics. The modulus of a real number is its positive value, shown by placing the number between vertical lines: thus |–2| = |+2| = 2. The modulus (or absolute value) of a complex number z, where z = x + iy, is defined as √(x ² + y ²). If z is represented by a point in an Argand diagram, then its modulus r, is the distance from the origin to that point. Again, the term modulus sometimes refers to a constant of proportionality. In logarithms, if log_ax = k log_bx, where a and b are different bases, k is known as the modulus.