Breakdown voltage
The breakdown voltage is a property of electrical insulators. When the voltage across an insulator is higher than the breakdown voltage, electrical breakdown changes the insulator into an electrical conductor. Breakdown voltage depends on the specific shape and structure of an object, and is not an intrinsic property of a material.
Breakdown voltage is an important property of semiconductor devices such as diodes and transistors. Above the breakdown voltage, these devices can be damaged by the sudden increase in electrical current. Zener diodes are designed to make use of the breakdown voltage to act as voltage regulators.