| L | Fifty (in Roman Numerals) -Label - Lap - Large - Laser (US Military Aircraft Basic Mission Designation) - Latin - Left -Litre -Low (transmissions) | - | Astronomy |
| L.S. | Lectori Salutem (Latin | - | Astronomy |
| LA | Lanthanum | - | Astronomy |
| LA | Laos (FIPS 10-4 Country Code; ISO 3166 Digram) -Los Angeles -Louisiana (postal Symbol) | - | Astronomy |
| LA | Latin Language (ISO 639-1 Code) | - | Astronomy |
| LAAS | Local Area Augmentation System - Los Angeles Astronomical Society | - | Astronomy |
| LAB | Logistics Assault Base | - | Astronomy |
| LABVIEW | Laboratory Virtual Instrumentation Engineering Workbench | - | Astronomy |
| LACMA | Los Angeles County Museum Of Art | - | Astronomy |
| LAD | Laser Aiming Device | - | Astronomy |
| LADW | Local Air Defence Warning | - | Astronomy |
| LAESI | Local Authority & Emergency Service Information | - | Astronomy |
| LAK | Laotian Kip (ISO 4217 Currency Code) | - | Astronomy |
| LAMP | Linux | - | Astronomy |
| LAN | Local Area Network | - | Astronomy |
| LANL | Los Alamos National Laboratory | - | Astronomy |
| LAO | Lao Language (ISO 639-2 Code) | - | Astronomy |
| LAO | Laos (ISO 3166 Trigram) | - | Astronomy |
| LAPD | Los Angeles Police Department | - | Astronomy |
| LAR | Light Armoured Reconnaissance - Logistics Assistance Representative | - | Astronomy |
| LARC | Livermore Advanced Research Computer (cf. LLNL) | - | Astronomy |
| LARP | Live-Action Role-Playing | - | Astronomy |
| LAS | McCarran International Airport (Las Vegas | - | Astronomy |
| LASER | Light Amplification By Stimulated Emission Of Radiation (cf. Maser) | - | Astronomy |
| LAT | Lowest Astronomical Tide (nautical Charts) | - | Astronomy |
| LAT | Latin Language (ISO 639-2 Code) | - | Astronomy |
| LATA | Local Access Transport Area | - | Astronomy |
| LAV | Land Assault Vehicle - Light Armoured Vehicle - Lymphadenopathy-Associated Virus | - | Astronomy |
| LAV | Latvian Language (ISO 639-2 Code) | - | Astronomy |
| LAW | Light Antitank Weapon | - | Astronomy |
| LAX | Los Angeles International Airport | - | Astronomy |
| LB | Lebanon (ISO 3166 Digram) | - | Astronomy |
| LB | Pound (Latin Librum) - Luxembourgish Language (ISO 639-1 Code) | - | Astronomy |
| LBH | Light Battlefield Helicopter - Lyman-Birge-Hopfield Bands | - | Astronomy |
| LBJ | Lady Bird Johnson - Light Bulb Joke - Little Beagle Johnson (LBJ's Dog) - Lyndon Baines Johnson | - | Astronomy |
| LBN | Lebanon (ISO 3166 Trigram) | - | Astronomy |
| LBNL | Lawrence Berkeley National Laboratory | - | Astronomy |
| LBP | Lebanese Pound (ISO 4217 Currency Code) | - | Astronomy |
| LBR | Liberia (ISO 3166 Trigram) | - | Astronomy |
| LBS | Location-Based Services | - | Astronomy |
| LBW | Leg Before Wicket | - | Astronomy |
| LBY | Libya (ISO 3166 Trigram) | - | Astronomy |
| LC | Line Of Contact -Saint Lucia (ISO 3166 Digram) | - | Astronomy |
| LC2IEDM OR LC?IEDM | Land C2IEDM (q.v.) | - | Astronomy |
| LCA | Saint Lucia (ISO 3166 Trigram) | - | Astronomy |
| LCC | Land Component Commander | - | Astronomy |
| LCCP | Light Contingency Communications Package | - | Astronomy |
| LCD | Liquid Crystal Display | - | Astronomy |
| LCE | Leaving Certificate Examination - Load Carrying Equipment - London Commodity Exchange | - | Astronomy |
| LCM | Least/Lowest Common Multiple | - | Astronomy |
| LCOL | Lieutenant-Colonel (Canada | - | Astronomy |
| LD | Laser Designator - Limited Deployment - Line Of Departure | - | Astronomy |
| LDA | Lateral Drift Apparatus (paratroops) | - | Astronomy |
| LDAP | Lightweight Directory Access Protocol (pronounced Ell-dap) | - | Astronomy |
| LDC | Lesser Developing/Developed Country | - | Astronomy |
| LDL | Low-Density Lipoprotein | - | Astronomy |
| LDMOS | Lateral Double-diffused MOS Transistor (ell-dee-moss) | - | Astronomy |
| LDS | Latter Day Saint - Liberal Democracy Of Slovenia | - | Astronomy |
| LDV | Local Defence Volunteers (British Home Guard) | - | Astronomy |
| LE | Lebanon (FIPS 10-4 Country Code) | - | Astronomy |
| LEC | Local Exchange Carrier | - | Astronomy |
| LED | Light-Emitting Diode | - | Astronomy |
| LEGAD | Legal Advice | - | Astronomy |
| LEMOSS | Long-Endurance MObile Submarine Simulator | - | Astronomy |
| LEN | Large Extension Node | - | Astronomy |
| LEO | Low Earth Orbit | - | Astronomy |
| LEP | Large Electron-Positron Collider | - | Astronomy |
| LER | Loss-Exchange Ratio | - | Astronomy |
| LEU | Low-Enriched Uranium | - | Astronomy |
| LF | Low Frequency | - | Astronomy |
| LG | Latvia (FIPS 10-4 Country Code) | - | Astronomy |
| LG | Luganda Language (ISO 639-1 Code) | - | Astronomy |
| LGB | Lesbian | - | Astronomy |
| LGBT | Lesbian | - | Astronomy |
| LGM | Little Green Men | - | Astronomy |
| LGS | Landsat Ground Station | - | Astronomy |
| LH | Lithuania (FIPS 10-4 Country Code) -Luteinising Hormone | - | Astronomy |
| LHC | Large Hadron Collider | - | Astronomy |
| LHD | Litterarum Humaniorum Doctor (Latin | - | Astronomy |
| LHS | Left Hand Side | - | Astronomy |
| LI | Fifty-one (in Roman Numerals) -Liberia (FIPS 10-4 Country Code) - Liechtenstein (ISO 3166 Digram) | - | Astronomy |
| LI | Limburgish Language (ISO 639-1 Code) | - | Astronomy |
| LI | Lithium | - | Astronomy |
| LIBS | Laser Induced Breakdown Spectroscopy | - | Astronomy |
| LIE | Liechtenstein (ISO 3166 Trigram) | - | Astronomy |
| LIFO | Last In | - | Astronomy |
| LIGO | Laser Interferometer Gravitational Wave Observatory | - | Astronomy |
| LIM | Limburgish Language (ISO 639-2 Code) | - | Astronomy |
| LIN | Lingala Language (ISO 639-2 Code) | - | Astronomy |
| LINEAR | Lincoln Near-Earth Asteroid Research | - | Astronomy |
| LISA | Laser Interferometer Space Antenna | - | Astronomy |
| LIT | Lithuanian Language (ISO 639-2 Code) | - | Astronomy |
| LIVE | Liquid Inertial Vibration Eliminator | - | Astronomy |
| LJ | La Jolla - Larry Johnson - LaserJet - Library Journal - Linux Journal - LiveJournal - Ljubljana - Lord Justice Of Appeal -Sierra National Airlines (IATA Code) | - | Astronomy |
| LJJ | Lord Justices Of Appeal | - | Astronomy |
| LK | Sri Lanka (ISO 3166 Digram) | - | Astronomy |
| LKA | Sri Lanka (ISO 3166 Trigram) | - | Astronomy |
| LKR | Sri Lanka Rupee (ISO 4217 Currency Code) | - | Astronomy |
| LL | Land Line (telephone) - Last Log - Late Latin - Left Limit - Lex Luthor (Superman Character) - Light Line - Limited Liability - Linked List - Little League | - | Astronomy |
| LLAD | Low Level Air Defence | - | Astronomy |
