Natural
A sign which restores a letter to its place in the natural scale. In the ancient system of music the only changeable note in the scale was B. The sign for that sound was 2, the old form of the letter; it signified the sound we call B flat and was called B rotundum, i. e., round B. When it was to be raised a half tone a line was drawn downward at the right side, thus, and it was called B quadratum, i. e., square B. In our modern music these have been retained as the signs for flat and natural.