Which material is characterized by electrical conductivity that falls between a conductor and an insulator?

The material characterized by electrical conductivity that falls between a conductor and an insulator is the semiconductor. Semiconductors possess unique properties that allow them to conduct electricity under certain conditions, unlike conductors, which allow easy flow of electric current, and insulators, which do not conduct electricity at all.

Semiconductors have a conductivity level that can be modified by introducing impurities, a process known as doping. This ability to control conductivity makes them essential for modern electronics, including diodes, transistors, and integrated circuits. They can behave as conductors in some situations, especially when exposed to heat or light, while still having the properties of insulators under other conditions. This dual nature allows for the design of a wide range of electronic devices that can switch between on and off states efficiently.

In summary, the semiconductor's unique position between conductors and insulators, along with its tunable conductivity, is what defines its important role in electronics and other applications.