stave
A set of five horizontal lines on which musical notation is written, also called a staff.
In Depth
The stave (plural: staves) or staff is the foundation of Western musical notation — five horizontal lines and four spaces on which notes are placed to indicate pitch. Higher positions represent higher pitches. A clef at the beginning fixes the exact pitch mapping: the treble clef assigns G4 to the second line, the bass clef assigns F3 to the fourth line.
Notes that fall above or below the stave are written on short additional lines called ledger lines. For instruments with very wide ranges, two staves are used simultaneously — a grand staff for piano combines treble and bass clefs connected by a brace. The five-line staff was standardised by the 11th century, replacing earlier systems with varying numbers of lines.
Before the five-line staff became standard, notation systems used anywhere from one to eleven lines. Guido d'Arezzo's four-line staff for plainchant is still used for Gregorian chant today.