n. (also d) (pl. Ds or D's)
1 the fourth letter of the alphabet.
2 Mus. the second note of the diatonic scale of C major.
3 (as a Roman numeral) 500.
4 = DEE.
5 the fourth highest class or category (of academic marks etc.).
symb. Chem. the element deuterium.
abbr. (also D.)
1 US Democrat.
2 dimension (3-D).
Useful english dictionary. 2012.