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, ld(x) = log ₂(x), from the Latin logarithmus dualis.
• Lunar distance, 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
• 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

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

LD can also refer to:

• 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.

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.