Definition: The nominal of the second tone in the model major scale (that in
C), or of the fourth tone in the relative minor scale of C (that in A
minor), or of the key tone in the relative minor of F.
Definition: As a numeral D stands for 500. in this use it is not the initial
of any word, or even strictly a letter, but one half of the sign / (or
/ ) the original Tuscan numeral for 1000.