The dual of an impedance Z {\displaystyle Z} is its reciprocal, or algebraic inverse Z ′ = 1 Z {\displaystyle Z'={\frac {1}{Z}}} . For this reason the dual impedance is also called the inverse impedance. Another way of stating this is that the dual of Z {\displaystyle Z} is the admittance Y ′ = Z {\displaystyle Y'=Z} .