A relationship between two values that characterizes the behaviour of a device, circuit, or apparatus. The relations are most commonly produced for transistors and two-port networks. They are usually plotted in the form of families of graphs (characteristic curves) relating the currents obtained to the voltages applied for a range of operating conditions.

The electrode characteristic shows the relationship between current and voltage at an electrode of the device, for example drain current versus drain voltage in a field-effect transistor. The transfer characteristic shows the relationship between the current (or voltage) at one electrode and the voltage (or current) at a different electrode, for example drain current versus gate voltage in a FET. The static characteristic shows, for example, collector current versus base voltage in a bipolar junction transistor, all other applied voltages being held constant, i.e. under static conditions. The dynamic characteristic relates the current from one electrode and the voltage on another, under dynamic conditions. See also transfer parameters.