A natural is any note that is not a sharp or a flat and which is thus represented by the white keys on a piano or organ keyboard. In standard music notation the natural symbol (♮) is placed on the corresponding line or space on a staff to cancel a sharp or flat from either an accidental applied to a preceding note in the same measure or from the key signature. When used with regard to the key signature in particular, a natural can be considered as a type of accidental. As with other accidentals, a natural symbol usually also affects all repetitions of the note within the measure in which it appears as well as the same note in other octaves within the measure.