In electronics, the word dual refers to two devices or circuits that have mathematical descriptions that are identical except that voltages in one correspond to currents in the other, and vice versa. For example:

• a resistance is the dual of a conductance;
• two resistances in series are the dual of two conductances in parallel;
• a capacitor is the dual of an inductor;
• Kirchoff's current law is the dual of Kirchoff's voltage law.

For other meanings of the word see duality.