Amp is short for amplifier, a device that makes sounds louder. When a guitarist plugs an electric guitar into an amp, it boosts the quiet vibrations of the strings into music powerful enough to fill an auditorium. Rock bands use massive amps to project their sound to thousands of fans, while a student practicing at home might use a small amp that fits on a desk.

The word works as both a noun and a verb. As a noun, you might say, “Turn up the amp!” As a verb, to amp something means to increase its intensity or energy. Before a big game, a coach might amp up the team with an inspiring speech. You might feel amped (excited and energized) about your birthday party or the last day of school.

Amp is also short for ampere, the unit that measures electric current, named after French physicist André-Marie Ampère. Electricians use amps to describe how much electricity flows through a wire, like how gallons per minute measure water flow. A typical house circuit handles 15 or 20 amps, while a phone charger uses just one or two amps.