Definition of: d, D

(dē) noun plural d's, D's or Ds, ds, dees (dēz)
1. The fourth letter of the English alphabet, from Phoenician daleth, through the Hebrew daleth, Greek delta, Roman D.
2. The sound of the letter d, usually a voiced alveolar stop. See ALPHABET.
—symbol
1. In Roman notation, the numeral 500. See under NUMERAL.
2. Music a The second note in the natural scale of C; re. b The pitch of this tone, or the written note representing it. c The scale built upon D.
3. Differentiation or, in algebra, a known quantity.
4. Anything shaped like a D or a half circle, as the iron loop on a saddle to which articles are attached.
5. Pence (d., from Latin denarii) in English money.
6. Chem. Deuterium.