Electrical conductance (G) is the reciprocal of electrical resistance (i.e., 1/R). The SI unit of conductance is the siemens, formerly (in MKS units) called the mho or reciprocal ohm. See also conductivity.
Electrical conductance (symbolized by G) is a useful concept especially when dealing with parallel DC (direct current) circuits. For a similar reason, the reciprocal of the impedance, defined as the admittance, is useful in handling parallel AC (alternating current) circuits. In the case of parallel AC circuits, G reduces to 1/R when purely resistive elements are present. In the general case when there are both resistive and reactive elements, the expression for G is R/(R2 + X2), where X is the reactance.