The magnetic flux linkage, Φ, is generalized from the circuit characteristic of an inductor.

This relationship is only valid for linear (non-saturated) regions of the magnetic flux linkage and current relationship.

According to the original 1971 definition, the memristor was the fourth fundamental circuit element, forming a non-linear relationship between electric charge and magnetic flux linkage.

The memristor was originally defined in terms of a non-linear functional relationship between magnetic flux linkage Φ(t) and the amount of electric charge that has flowed, q(t):