1. In general, the voltage at which a particular characteristic of an electronic device first appears.

2. The voltage at which conduction of current begins in a pn junction.

3. The voltage at which channel formation occurs in a metal oxide semiconductor field-effect transistor.

4. The voltage at which a solid-state lamp begins to emit light.

The lowest voltage at which all pulses produced in a Geiger counter by any ionizing event are of the same size, regardless of the size of the initial ionizing event.