A symbol placed by a note signifying that the note should be played unaltered as opposed to the sharp or flat of the note. This symbol is usually seen only where an accidental such as a sharp or flat is expected, thus assuring the performer that the note should be played without such an accidental.
The natural symbol alters the pitch of the note to which it is attached as well as any subsequent occurrence of the same note (identical line or space) in the same measure. Notes with the same pitch name, but a higher or lower octave, are not affected. Any note with a natural that also has a tie across a barline carries the natural to the note on the other side of the barline. Notes in the new measure that are not tied to altered notes from the previous measure revert to their original pitch and are performed using the current key signature.