In music theory, a natural is an accidental which cancels previous accidentals and represents the unaltered pitch of a note[1].
A note is natural when it is neither flat nor sharp (nor double-flat or double-sharp either). Natural notes are the notes A, B, C, D, E, F, and G, and are represented by the white notes on the keyboard of a piano or organ. On a modern concert harp, the middle position of the seven pedals which alter the tuning of the strings gives the natural pitch for each string.
The scale of C major is sometimes regarded as the central or natural or basic major scale, because all of its notes are natural notes, whereas every other major scale has at least one sharp or flat in it.
The notes F-flat, C-flat, E-sharp, B-sharp, and most notes inflected by double-flats and double-sharps correspond in pitch with natural notes; but they are not regarded as natural notes, but rather as enharmonic equivalents of them, and are just as much chromatically-inflected notes as the majority of sharpened and flattened notes which are represented by black notes on a keyboard.
In musical notation, a natural sign (♮) is an accidental sign used to cancel a flat or sharp from either a preceding note or the key signature. If a bar contains a double sharp or double flat accidental and the composer wishes to denote the same note with only a single sharp or flat, a natural sign traditionally precedes the (single) sharp or flat symbol. Naturals are assumed (by default) in key signatures and mentioned only in key signature changes.
The Unicode character MUSIC NATURAL SIGN '♮' (U+266E) should display as a natural sign. Its HTML entity is ♮.