Rest
You have to listen to the notes she's not playing.
— Lisa Simpson, The Simpsons, 1998
A rest is a gap between notes. Its length can be described the same as a note's length, as a fraction of a bar.
Music theory: Arpeggio | Block chord | Broken chord | Circle of fifths | Interval | Music | Pitched tempos | Polymetre and polyrhythm | Rest | Swing | Velocity