What type of component is often used as an adjustable volume control?

A potentiometer is a type of variable resistor equipped with three terminals and a sliding or rotating contact. This physical adjustment allows the user to manually change the resistance, making it the standard component for user-adjustable controls like a radio's volume dial. Fixed and power resistors have a static, unchangeable resistance value, meaning they cannot be used to dynamically adjust audio levels. A transformer is used to step AC voltage up or down or to match impedances, not to serve as an adjustable knob for a user.