1. contraction of had:I was glad they'd gone.

  2. contraction of did:Where'd they go?

  1. contraction of should or would:He'd like to go. I'd like to remind you of your promise.

  2. contraction of -ed:She OK'd the plan.

Other definitions for d' (2 of 12)


  1. de (used in French names as an elided form of de): Charles Louis d'Albert.

  2. di (used in Italian names as an elided form of di): Gabriele d'Annunzio.

Other definitions for d' (3 of 12)


  1. Informal. contraction of do or did before you:How d'you like your eggs cooked? D'you go to the movies last night?

Other definitions for D (4 of 12)


or d

[ dee ]

noun,plural D's or Ds, d's or ds.
  1. the fourth letter of the English alphabet, a consonant.

  2. any spoken sound represented by the letter D or d, as in dog, ladder, ladle, or pulled.

  1. something having the shape of a D.

  2. a written or printed representation of the letter D or d.

  3. a device, as a printer's type, for reproducing the letter D or d.

Other definitions for D (5 of 12)


  1. Electricity. debye; debyes.

  2. deep.

  1. depth.

  2. divorced.

Other definitions for D (6 of 12)


  1. the fourth in order or in a series.

  2. (sometimes lowercase) (in some grading systems) a grade or mark, as in school or college, indicating the quality of a student's work as poor or barely passing.

  1. (sometimes lowercase) a classification, rating, or the like, indicating poor quality.

  2. Music.

    • the second tone in the scale of C major, or the fourth tone in the relative minor scale, A minor.

    • a string, key, or pipe tuned to this tone.

    • a written or printed note representing this tone.

    • (in the fixed system of solmization) the second tone of the scale of C major, called re.

    • the tonality having D as the tonic note.

  3. (sometimes lowercase) the Roman numeral for 500.: Compare Roman numerals.

  4. Chemistry. deuterium. : Also 2H

  5. Electricity.

    • electric displacement.

    • a battery size for 1.5 volt dry cells: diameter, 1.3 inches (3.3 centimeters); length, 2.4 inches (6 centimeters).

  6. Biochemistry. aspartic acid.

  7. a symbol for a shoe width size narrower than E and wider than C.

  8. a proportional brassiere cup size larger than C.

Other definitions for d- (7 of 12)


  1. Symbol, Biochemistry. (of a molecule) having a configuration resembling the dextrorotatory isomer of glyceraldehyde: always printed as a small capital, roman character (distinguished from l-).

  • Compare d-.

Other definitions for d- (8 of 12)


Symbol, Chemistry, Biochemistry.
  1. dextrorotatory; dextro- (distinguished from l-).

  • Compare d-.

Other definitions for d. (9 of 12)


  1. (in prescriptions) give.

Origin of d.

From the Latin word

Other definitions for d. (10 of 12)


  1. British. pence.

Origin of d.

From the Latin word denāriī

Other definitions for d. (11 of 12)


  1. date.

  2. daughter.

  1. day.

  2. deceased.

  3. deep.

  4. degree.

  5. delete.

  6. Physics. density.

  7. depth.

  8. deputy.

  9. dialect.

  10. dialectal.

  11. diameter.

  12. died.

  13. dime.

  14. dividend.

  15. dollar; dollars.

  16. dose.

  17. drachma.

Other definitions for D. (12 of 12)


  1. day.

  2. December.

  1. Democrat.

  2. Democratic.

  3. Physics. density.

  4. Deus.

  5. Deuteronomy.

  6. Doctor.

  7. dose.

  8. Dutch.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use 'd in a sentence

British Dictionary definitions for d (1 of 7)



/ (diː) /

nounplural d's, D's or Ds
  1. the fourth letter and third consonant of the modern English alphabet

  2. a speech sound represented by this letter, usually a voiced alveolar stop, as in dagger

  1. the semicircle on a billiards table having a radius of 11 1/2 inches and its straight edge in the middle of the baulk line

British Dictionary definitions for d (2 of 7)


symbol for
  1. physics density or relative density

  2. maths a small increment in a given variable or function: used to indicate a derivative of one variable with respect to another, as in d y /d x

British Dictionary definitions for 'd (3 of 7)


contraction of
  1. would or had: I'd; you'd

British Dictionary definitions for D (4 of 7)


abbreviation for
  1. Deutsch: indicating the serial number in the catalogue (1951) of the musical compositions of Schubert made by Otto Deutsch (1883–1967)

British Dictionary definitions for D (5 of 7)


symbol for
  1. music

    • a note having a frequency of 293.66 hertz (D above middle C) or this value multiplied or divided by any power of 2; the second note of the scale of C major

    • a key, string, or pipe producing this note

    • the major or minor key having this note as its tonic

  2. chem deuterium

  1. maths the first derivative of a function, as in D(x ³ + x ²) = 3 x ² + 2 x

  2. physics

    • dispersion

    • electric displacement

  3. aeronautics drag

    • a semiskilled or unskilled manual worker, or a trainee or apprentice to a skilled worker

    • (as modifier): D worker See also occupation groupings

  4. (Roman numeral) 500: See Roman numerals

abbreviation for
  1. Germany (international car registration)

    • Australian informal defence: I'm playing D in the match this afternoon

    • Australian informal defensive play

Origin of D

(for sense 8) from German Deutschland

British Dictionary definitions for d. (6 of 7)


abbreviation for
  1. (in animal pedigrees) dam

  2. daughter

  1. British currency penny or pennies

  2. diameter

  3. died

  4. dinar(s)

  5. dollar(s)

  6. drachma(s)

Origin of d.

(sense 3 and 6) Latin denarius

British Dictionary definitions for D. (7 of 7)


abbreviation for
  1. US politics Democrat(ic)

  2. government Department

  1. dinar(s)

  2. Don (a Spanish title)

  3. Duchess

  4. Duke

  5. (in the US and Canada) Doctor

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for d


  1. Abbreviation of diameter

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.