What is the definition of a semiconductor?

A semiconductor is defined as a material that has intermediate conductivity between conductors, like metals, and insulators, like rubber. This property is crucial because it allows semiconductors to control electrical current in devices, making them essential components in electronics such as diodes, transistors, and integrated circuits.

Semiconductors can conduct electricity more effectively than insulators under certain conditions (like the application of heat or the introduction of impurities, which are known as dopants), yet not as well as good conductors. This unique behavior enables a wide range of electronic applications, as they can switch between conducting and insulating states based on external factors, thus functioning effectively in circuits.

The other choices do not accurately reflect the defining characteristics of semiconductors. A semiconductor is specifically not always an insulator, nor does it have zero conductivity. The ability to conduct electricity at certain temperatures is a characteristic of many materials, but it is the intermediate conductivity feature that fundamentally defines semiconductors.