LD may refer to:

In science and mathematics:

  • Lethal dose#, where "#" represents the percentage of test organisms killed by a specific dosage (of drugs, radiation, etc.), e.g. half will die at LD50
  • The logarithm of base 2, from the Latin logarithmus dualis
  • Lunar distance (astronomy), the distance between the Earth and the Moon and a measure of navigation
  • Linkage disequilibrium, when distinct alleles appear together more often than by chance (thanks to founder effects, etc.) in genetics
  • lactate dehydrogenase, an enzyme in plants and animals
  • London dispersion forces, weak intermolecular forces

In technology:

  • Laser diode, semiconductor laser-emitting device
  • Laserdisc format, an obsolete optical disc video/data format and predecessor to Digital Video Disc (DVD)
  • ld (Unix), the linker command on Unix and Unix-like systems
  • Long distance, a telephone call to another area sufficiently far away to be charged at a higher rate
  • Loop Disconnect dialing
  • ld, an instruction on a Z80 CPU
  • Line Dubbed, a term for pirate copies with an audio track, which has been ripped from the line out connection of a projector
  • Ladder diagram (disambiguation), various meanings
  • Linz-Donawitz process, a widely used conversion process in steelmaking

In politics:

  • Liberal democracy, a form of government based on rule of the people (democracy) tempered by the rule of law and natural rights (liberalism)
  • A form of debate (Lincoln–Douglas debate)
  • Liberal Democrats A UK based liberal political party

In television:

  • Lorraine "L.D." Delacorte, a character from the Degrassi series played by Amanda Cook
  • Larry David, sometimes referred to as L.D. in the television show Curb Your Enthusiasm
  • Latin Disciples, the name of a gang in television series Day Break
  • Low-definition television (LDTV)

In music:

  • Little Doses, a Scottish alternative rock band
  • Luis Dubuc

In Contracts:

  • Liability Damage

LD can also refer to:

  • LD, the ISO 3166-2 code for Lakshadweep, India
  • LD, the code for Longford, Ireland
  • Liberian dollar, the currency of Liberia
  • Libyan dinar, the currency of Libya
  • Liberty dollar, the private currency by norfed
  • Licensed Dietician
  • Lincoln–Douglas debate, a form of debate
  • Line Drive, a trajectory-related inference and statistic of a batted ball in baseball
  • Little Diamond
  • Learning disability, a condition that can impair learning through standard methods
  • Lilian day, a variant of the Julian day
  • Lucid dreaming, a dream in which one is conscious of dreaming as it is happening
  • Long distance relationships
  • Lighting designer, the person in charge of lighting in theatre
  • Air Hong Kong and Linea Turistica Aerotuy, airlines with IATA code LD
  • Liquor drink, a drink composed of a Distilled beverage and a drink mixer
  • LD (cigarette), a brand of cigarette from the Gallaher Group
  • Living Dangerously, an ECW PPV
  • Louis-Dreyfus Group, a French commodities trading firm
  • Lynsey Dyer, an American freeskier and Big Mountain skier
  • Liquidated Damages, a figure in Contract Law
  • Listening device, used in covert investigations
  • LincsDriver, a car club in Lincoln, United Kingdom
  • Ludum Dare a rapid game development competition
  • Light Dragoons, a British Army cavalry regiment

Ld (Capital L with a lower case "d") is the abbreviated form of:

  • Lord, a peer of the realm in the United Kingdom
  • Lordi, a hard rock band