d

d is a Noun

Definition:

[1] The fourth letter of the English alphabet, and a vocal consonent. The English letter is from Latin, which is from Greek, which took it from Phoenician, the probable ultimate origin being Egyptian. It is related most nearly to t and th; as, Eng. deep, G. tief; Eng. daughter, G. tochter, Gr. duhitr. See Guide to Pronunciation, sq. root178, 179, 229.

[2] 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.

[3] 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