What is the definition of a diode?

A diode is defined as a device that allows current to flow in one direction. This is a fundamental characteristic of diodes, which are semiconductor devices that exhibit rectifying behavior, meaning they enable current to pass through them when they are forward-biased (allowing flow) and block current when they are reverse-biased (preventing flow). This unidirectional flow of electric current makes diodes essential components in electronic circuits for tasks such as signal modulation, power conversion, and protection against voltage spikes.

The other options describe different components or characteristics relevant to electronics but do not capture the essential function of a diode. For example, while a device that stores charge temporarily refers to capacitors, and non-metallic materials used in semiconductor devices pertains to the broader context of materials science, they do not define the operating principle of a diode. Similarly, while metal oxide semiconductors are a significant type of semiconductor technology, they do not specifically identify the role or function of a diode.