'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 √(x2 + y2). 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 logax = k logbx, where a and b are different bases, k is known as the modulus.