tempo
The speed at which a piece of music is played.
In Depth
Tempo is the speed at which music is performed, typically indicated by Italian terms (adagio, allegro, presto) or precise metronome markings (♩= 120 means 120 quarter-note beats per minute). Together with dynamics and articulation, tempo is one of the primary ways performers shape and interpret music.
The metronome, patented by Johann Maelzel in 1816, gave composers the ability to specify exact tempos for the first time. Before that, tempo was a matter of convention, experience, and musical judgment. Even with metronome markings, tempo in practice is rarely rigid — subtle fluctuations are natural and expected, and different performers often take the same piece at notably different speeds.
Beethoven was one of the first composers to use the metronome (invented by his contemporary Maelzel), but many of his metronome markings are considered controversially fast — performers have debated them for 200 years.