What is defined as the opposition to a change in current in an AC circuit?

The correct answer is inductance. Inductance is the property of an electrical circuit that opposes a change in current. In an alternating current (AC) circuit, inductors resist variations in current flow due to the magnetic field generated around them when current passes through. This characteristic is crucial because it causes the current and voltage to be out of phase in an inductor, meaning that when the current is at its maximum, the voltage is not, and vice versa.

This opposition to changes in current can be quantitatively described by the formula for inductance, which contributes to the overall impedance in an AC circuit. In contrast, capacitance relates to the ability to store electric charge, while rectification is the process of converting AC to direct current (DC). Inductive reactance specifically refers to the opposition to the change in current that an inductor presents at a particular frequency, but "inductance" encapsulates the broader concept of how inductors inherently react to current changes.