LD

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:

In Contracts:

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