LD

LD can mean:

In science and mathematics:
*Lethal dose, the percentage of test organisms killed by a specific dosage (of drugs, radiation, etc.).
*The logarithm of base 2, $mathrm\{ld\}(x)=log\_2(x)$, from the Latin "logarithmus dualis".
*Lunar distance, the distance between the Earth and the Moon and a measure of navigation.
*Linkage disequilibrium, when seemingly independent alleles have different rates of appearance (thanks to fitness concerns, etc.) in genetics.
*lactate dehydrogenase
*London dispersion forces

In technology:
*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.
*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

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).

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

In music:
*Luis Dubuc

LD can also refer to:
*Liberian dollar, the currency of Liberia
*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.
*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, a ECW PPV
*Louis-Dreyfus Group, a French commodities trading firm

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