- The indicated output of a device measuring an electrical quantity, when there is no signal present. Also, such a zero reading after calibration.
- An indicated output of zero for a device measuring an electrical quantity, when a given input value, such as a specific voltage, must be applied to obtain said indication of zero.
- An electric potential which is arbitrarily considered to be zero, such as that of the ground.
- For a rotating device, such as a synchro, the reference point from which angles are measured.