In Western music notation, the staff (plural is staves) is a set of five lines and four spaces, each of which represents a different pitch. Appropriate music symbols, depending upon the intended effect, are placed on the staff according to their corresponding pitch or function. Musical notes are placed by pitch, percussion notes are placed by instrument, and rests and other symbols are placed by convention.

The absolute pitch of each line for a non-percussive stave is determined by the placement of an appropriate clef symbol at the appropriate vertical position on the left-hand side of the staff. For example, the treble clef, also known as the G clef, is placed upon the second line (counting upwards), fixing that line as the pitch first G above ‘middle C’.

The lines and spaces are numbered from bottom to top; the bottom line is the first line and the top line is the fifth line.