d

  1. 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.
  2. 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.