D (disambiguation)

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D is the fourth letter of the Latin alphabet. It can also refer to the following:

Business and economy[edit]


  • D, the name of various programming languages:
  • D, the "Minimal Protection" security division in the TCSEC
  • d (short for daemon), a suffix often added to the name of a computer program that runs as a background process
  • .d, a common pathname component suffix for a directory for a program or subsystem on POSIX and POSIX-like systems; for example "/etc/init.d" would be a directory which contains files associated with the init program.
  • .d, a file format used for Agilent MassHunter mass spectrometry software

Entertainment and film[edit]




Chemistry and biology[edit]

  • D, the symbol for aspartic acid in biochemistry
  • D, the symbol of deuterium, an isotope of hydrogen, in chemistry
  • Vitamin D
  • ATC code D Dermatologicals, a section of the Anatomical Therapeutic Chemical Classification System




  • d, the symbol for the total differential operator (partial differentials use ∂)
  • D, often used as a digit meaning thirteen in hexadecimal and other positional numeral systems with a radix of 14 or greater
  • Blackboard bold \mathbb{D}, representing the unit disk in the complex plane, or the decimal fractions (see number)
  • d, often a variable for the diameter of a circle in geometry
  • D and d, the derivative operators
  • D, the number five hundred in Roman numerals


  • \mathbf{D}, the recommended symbol for electric displacement field
  • d, the recommended symbol for: thickness, diameter, relative density (mechanics), lattice plane spacing (solid state physics), and degeneracy of vibrational mode, in molecular spectroscopy
  • d, the symbol of the deuteron in particle physics
  • D, the symbol for debye, a unit of electrical dipole moment
  • D battery, a standard size dry cell battery in electronics
  • D, the name of mesons containing charm quarks in particle physics
  • D, the recommended symbol for diffusion coefficient in molecular physics
  • In solid state physics:
  • D, the standard abbreviation for an electronic diode, used e.g. in circuit diagrams

Other science[edit]

  • D region, part of the ionosphere in earth science
  • D, standing for demand in economics
  • d (deci-), the SI prefix meaning one tenth, 10−1
  • d, the symbol for day in metrology
  • d', psychophysical discriminability

Other uses[edit]