d

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The fourth letter of the modern English alphabet.
2. n. Any of the speech sounds represented by the letter d.
3. n. The fourth in a series.
4. n. Something shaped like the letter D.
5. n. The lowest passing grade given to a student in a school or college.
6. n. Music The second tone in the scale of C major or the fourth tone in the relative minor scale.
7. n. Music A key or scale in which D is the tonic.
8. n. Music A written or printed note representing this tone.
9. n. Music A string, key, or pipe tuned to the pitch of this tone.
10. abbr. deuteron.
11. abbr. diameter.
12. abbr. differential.
13. abbr. down quark

Century Dictionary and Cyclopedia

1. The fourth letter and third consonant in the English alphabet: the corresponding character has the same position and the same value also in the Latin, Greek, and Phenician alphabets, from which it comes to us. (See A.) The scheme of corresponding characters (compare the preceding letters) is as follows: The sound which the character has from the beginning been used to represent is the sonant or voiced mute (or check, stop, contact sound) corresponding to t as surd or breathed, and to n as nasal. (See the terms used and the letters referred to.) It is generally called a “dental,” but with only a conventional propriety, since the teeth bear no part in its production. It involves a closure of the tip of the tongue against the roof of the mouth at a point near to, or even touching, the upper front teeth (while an intonated or voiced current of air is driven during the closure into the cavity of the mouth, as in the case of the other sonant mutes); it is, then, rather a tongue-tip sound, or a front lingual. Sounds closely akin to it are made with different parts of the front tongue against different parts of the forward palate; hence the d is somewhat variously colored in various languages, and in some there are two diverse d's, or even more than two. The d, as belonging to the fundamental or Germanic part of our language, has taken the place of a more original aspirate, namely, Sanskrit dh, Greek θ, Latin oftenest f: thus, English door = Sanskrit dhura = Greek θύρα = Latin fores. Its regular correspondent in German is t: thus, tor (usually written thor) = English door; but, under special conditions, also a d: thus, German ende = English end; German gold = English gold. The German d regularly corresponds to English th. (See th.) Our d has no variety of values; it is, however, not seldom made surd, or pronounced as t, as in picked, tipped, kissed, and the like, being in older words of this kind a substitute, for mechanical uniformity of spelling, for earlier t; missed being formerly mist, miste, Anglo-Saxon miste; kissed, formerly kist, kiste, Anglo-Saxon cyste, etc. See -d = -ed, -d = -ed.
2. As a numeral, in the Roman system, D stands for 500; when a dash or stroke is placed over it, as D, it stands for 5,000.
3. As a symbol: In music: The second tone, or re, of the scale of C. The ratio between the vibration-numbers of these two tones, when in the relation of do and re, is . The tone above bass C is represented by D, the octave above by d, etc. See C, 3.
4. A note which represents this tone. On the treble staff D stands on the first added space below, or on the fourth line ; and on the bass staff it stands on the third line, or on the second added space above
5. The key-note of the key of two sharps .
6. On the keyboard of the organ or pianoforte, the white key or digital included in each group of two black keys.
7. The string in a stringed instrument that is tuned to the tone D, as the third string of the violin, etc. In chem., D is the symbol of didymium.
8. In mathematics, d is the sign of differentiation, ∂ of partial differentiation, δ of variation, D of derivation (commonly in the sense of taking the differential coefficient), ▵ of differencing, and ⾿ of the Hamiltonian operator. Many analysts avoid the use of the letter in other senses than these. A letter subjoined to any of these signs of operation shows what is taken as the independent variable, and exponents show the number of times the operations are to be performed. Differentiation (especially when relative to the time) was formerly indicated in England by a dot over the sign of the quantity to be differentiated, this being the notation of Newton's fluxional calculus.
9. In the mnemonic words of logic, the sign of reduction to darii.
10. As an abbreviation: In Eng. reckoning (d. or d.), an abbreviation of denarius, the original name for the English penny: as, £ s. d., pounds, shillings, and pence; 2s. 1d., two shillings and one penny.
11. Before a date (d.), an abbreviation of died.
12. In dental formulas, an abbreviation of deciduous, prefixed without a period to the letters i, c, and m: thus, di., deciduous incisor; dc., deciduous canine; dm., deciduous molar: all being teeth of the milk-dentition of a diphyodont mammal. Thus, the milk-or deciduous dentition of a child is expressed by the formula
13. or, more simply, taking one half of each jaw only, di. , dc. , dm. . In either case the numbers above the line are those of the upper teeth, and those below the line of the under teeth. See dental.
14. In anatomy and ichthyology (d. or D.), an abbreviation of dorsal (vertebra or fin, respectively).
15. In a ship's logbook (d.), an abbreviation of drizzling.
16. A form of -ed, -ed, in certain words. See -ed, -ed.
17. n. In music, an abbreviation of da capo.
18. n. An abbreviation of Latin (ML.) divinitatis doctor, Doctor of Divinity.
19. An abbreviation of the Latin defensor fidei, defender of the faith. See defender.
20. An abbreviation of the Latin Dei gratia, by the grace of God.
21. n. In music, an abbreviation of destra mano (which see).
22. n. Abbreviations of Doctor of Music.
23. An abbreviation of dead-reckoning.
24. n. An abbreviation of dal segno.
25. n. An abbreviation of the Latin Deo volente, God willing. See Deo volente.
26. In music: Also, the key-note of the minor key medieval music, the final of the Dorian and Hypodorian modes.
27. In chem.: d- before certain compounds has reference to their behavior toward polarized light, namely, to their dextrorotation, as distinguished from their inaction (i-) or levorotation (l-).
28. In mathematics: D is also used for the number denoting the deficiency of a curve (what its number of double points lacks of the maximum).
29. As an abbreviation: In law (D.), an abbreviation of Decree, Decret, Dictum.
30. In medicine (d.), an abbreviation of: diopter or dioptric;
31. dexter (right.);
32. divide (in prescriptions).
33. (D.) Of Democrat, Deus (God), Dominus (Lord), Dutch; (d.) of daughter, delete (cancel), density.
34. Short for damn (often printed d—).
35. Any mechanical device or appliance which resembles the letter D; specifically, in a harness, a loop of metal which has a straight bar joined at each end to a semicircular loop: used as a support for a strap. Also written dee. See D-trap and D-valve.
36. n. An abbreviation of Doomsday Book.
37. n. An abbreviation of direct current;
38. n. of District Court;
39. n. of District of Columbia;
40. n. of Deputy Consul;
41. n. of Divus Cæsar (the divine Cæsar).
42. n. An abbreviation of Dynamical Engineer, a degree conferred at the completion of a graduate course in mechanical engineering.
43. An abbreviation of Dean of the Faculty.
44. An abbreviation of deadhead or deadheaded.
45. n. An abbreviation of Deputy Lieutenant;
46. n. of Doctor of Law, a degree equivalent to D. C. L.
47. n. of Doctor of Literature, a degree equivalent to D. Lit.
48. An abbreviation of Doctor of Oratory
49. of Doctor of Osteopathy.
50. An abbreviation of Doctor of Pharmacy.
51. In electricity, an abbreviation for double pole.
52. n. An abbreviation of Doctor of Science.
53. n. Abbreviations of Doctor of Theology.
54. n. An abbreviation of delirium tremens.
55. n. In electricity, of double-throw: as, a d. t. switch.

Wiktionary

1. n. The fourth letter of the basic modern Latin alphabet.
2. n. cardinal number five hundred (500).
3. n. mathematics the differential of a quantity
4. n. voiced alveolar plosive
5. n. The fourth letter of the English alphabet, called dee and written in the Latin script.
6. n. The ordinal number fourth, derived from this letter of the English alphabet, called dee and written in the Latin script.
7. abbr. died, death.
8. abbr. cricket declared; also abbreviated as dec
9. n. until February 1971 a British penny; an old penny (the modern decimal penny being abbreviated p).
10. n. games, infix dice to use in a diceroll
11. n. penny, a measure of the size of nails

GNU Webster's 1913

1. The fourth letter of the English alphabet, and a vocal consonant. The English letter is from Latin, which is from Greek, which took it from Phœnician, the probable ultimate origin being Egyptian. It is related most nearly to t and th. See Guide to Pronunciation, √178, 179, 229.
2. (Mus.) 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 � (or � ) the original Tuscan numeral for 1000.

WordNet 3.0

1. n. the 4th letter of the Roman alphabet
2. adj. denoting a quantity consisting of 500 items or units
3. n. a fat-soluble vitamin that prevents rickets
4. n. the cardinal number that is the product of one hundred and five