How is wire size typically expressed?

Wire size is typically expressed in terms of gauge, which is a measurement system that indicates the thickness of the wire. The gauge system provides a standardized way to categorize the diameter of wires, allowing for consistent specifications across different applications and industries. Each gauge number corresponds to a specific wire diameter; as the gauge number decreases, the wire diameter increases. This system is particularly useful in electrical applications, where the wire gauge can directly affect the wire's conductivity, resistance, and the amount of current it can safely carry.

On the other hand, options like diameter and thickness refer to specific physical measurements, but they do not convey the standardized categorization that gauge does. Length is a separate dimension that pertains to how long the wire is, not its thickness or size. Thus, gauge is the most precise and commonly accepted way to identify wire size in various technical and industrial contexts.