- The relationship between an input magnitude, such as a voltage, to an output magnitude, such as a current. Also, the relation between an output magnitude, such as a voltage, to an input magnitude, such as a current. Usually expressed as a graph or plot.
- The relationship of the voltage of one electrode to the current of another, with all other electrodes having a fixed voltage.
- The relationship between the illumination incident upon a camera tube and the output signal current, under specified conditions.