The staff or stave (plural: staves) indicates the set of lines used for the notation of notes of different pitches. The five-line stave is in general use, with a four-line stave used for plainchant. Staves of other numbers of lines were once used. The system, with coloured lines for C and for F, followed principles suggested first by Guido of Arezzo in the 11th century. Staff notation is the system of notation that uses the stave.