| LTER | Long-Term Ecological Research | In English | → Ecology |
| LTG | Linear Tangent Guidance | In English | |
| LTH | Lethality and Target Hardening | In English | |
| LTHIS | Laboratory Test Hardware Inventory Status | In English | → Hardware |
| LTL | Linear Temporal Logic | In English | → Software → Mathematics |
| LTM | Lead Time Matrix | In English | |
| LTM | Load Transformation Matrix | In English | |
| LTP | Long-term potentiation | In English | → Biological sciences |
| LTP | Low Temperature Physics | In English | → Serial publications, periodicals → Physics |
| LTPS | Low-Temperature Polycrystalline Silicon | In English | → Metallurgy |
| LTR | Laboratory Test Report | In English | |
| LTR | Long Terminal Repeat | In English | → Genetics |
| LTT | Laboratory of Thermal Turbomachines | In English | → Research institutes → Mechanical engineering |
| LTV | Lunar Transfer Vehicle | In English | → Vehicle engineering → Spaceflight engineering, astronautics |
| LTV | Loan-to-Value | In English | → Finance |
| LTVC | Linear Terminal Velocity Constraint | In English | |
| LTWA | Library of Tibetan Works & Archives | In English | → Libraries |
| LTWG | Launch Test Working Group | In English | → Vehicle engineering |
| LubEn | Lubrication Engineering | In English | → Serial publications, periodicals → 521 |
| LUG | Linux Users' Groups = GUL | Groupes d'Utilisateurs de Linux | In French |
In English | → Organizations and associations → Operating systems |
| LUGOAL | Linux User Group Of ALgeria | In English | → Organizations and associations → Operating systems |
| LULAC | League of United Latin American Citizens | In English | → Organizations and associations |
| LULUCF | Land Use, Land Use Change and Forestry | In English | → Agricultural sciences → Forestry |
| LUMC | Leiden University Medical Center (www.lumc.nl) | In English | → Higher education, universities → Medicine |
| LUMO | Lowest Unoccupied Molecular Orbital | In English | → Nuclear, atomic, and molecular physics |
| LUPI | Laser Unequal Path Interferometer | In English | |
| LUPWT | Langley Unitary Plan Wind Tunnel | In English | |
| LUS | Liquid Upper Stage | In English | |
| LUSU | Laurentian University Staff Union = SEUL | Syndicat des Employés de l’Université Laurentienne | In French |
In English | → Organizations and associations → Labour, labour economics → Higher education, universities |
| LUT | Launch Umbilical Tower | In English | → Spaceflight engineering, astronautics |
| LUTEA | Land Use in Temperate East Asia | In English | → Ecology → Agricultural sciences |
| LUV | Large Unilamellar Vesicle | In English | → Biotechnology → Pharmacology, toxicology |
| LV | Lift Vector | In English | |
| LV | Low-Voltage | In English | → Electrical engineering |
| LV | Launch Vehicle | In English | → Vehicle engineering |
| LVCSR | Large Vocabulary Speech Recognition | In English | → Computer-based techniques → Linguistics |
| LVD | Low Voltage Directive | In English | → Electrical engineering |
| LVDC | Launch Vehicle Digital Computer | In English | → Hardware → Vehicle engineering |
| LVDT | Linear Variable Differential Transformer | In English | |
| LVDT | Linear Velocity Displacement Transducer | In English | |
| LVDT | Linear Voltage Differential Transformer | In English | → Electrical engineering |
| LVE | Low-Voltage Electronics | In English | → Electronics |
| LVE-CCC | Low Voltage Electrical Equipment Certification Coordination Committee | In English | → Electrical engineering |
| LVFRR | Launch Vehicle Flight Readiness Review | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| LVH | Left Ventricular Hypertrophy | In English | → Cardiology |
| LVIP | Launch Vehicle Integration Plan | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| LVIS | Logistics Verification Information System | In English | → Maintenance and logistics |
| LVO | Launch Vehicle Operations | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| LVP | Low-Voltage Pressure | In English | → Electrical engineering |
| LVPS | Low-Voltage Power Supply | In English | → Electrical engineering |
| LVR | Low-Voltage Release | In English | → Electrical engineering |
| LVRS | Lung Volume Reduction Surgery | In English | → Chest diseases |
| LVS | Linux Virtual Server | In English | → Operating systems → Networks, communication |
| LVS | Launch Vehicle Simulator | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| LVS | Launch Vehicle System | In English | → Vehicle engineering |
| LVSG | Launch Vehicle Study Group | In English | → Vehicle engineering |
| LVSSTS | Launch Vehicle Safety System Test Set | In English | → Vehicle engineering |
| LVT | LPAR Validation Tool | In English | → Software |
| LVTC | Launch Vehicle Test Conductor | In English | → Vehicle engineering |
| LWA | Local Wavefront Analyzer | In English | |
| LWBR | Light Water Breeder Reactor | In English | → Nuclear technology |
| LWCHWR | Light Water Cooled Heavy Water Reactor | In English | → Nuclear technology |
| LWD | Launch Window Display | In English | → Spaceflight engineering, astronautics |
| LWG | Logistics Working Group | In English | → Maintenance and logistics |
| LWGR | Light Water Cooled Graphite Reactor | In English | → Nuclear technology |
| LWIR | Long-Wavelength Infrared | In English | → Physics |
| LWS | Lightning Warning System | In English | → Meteorology, climatology |
| LWSH | Little Workers of the Sacred Hearts | In English | → Roman catholic church |
| M | Methionine = M | Metionina | In Catalan = M | Methionin | In German = M | Metionina | In Spanish = M | Metionino | In Esperanto = M | Méthionine | In French = M | 메티오닌 | In Korean = M | Metionin | In Indonesian = M | Metionina | In Italian = M | Metionin | In Croatian = M | מתיונין | In Hebrew = M | Metionīns | In Latvian = M | Methionin | In Letzeburgesh = M | Metioninas | In Lithuanian = M | Methionine | In Dutch = M | メチオニン | In Japanese = M | Metionin | In Norwegian = M | Metionina | In Polish = M | Metionina | In Portuguese = M | Метионин | In Russian = M | Метионин | In Serbian = M | Metioniini | In Finnish = M | Metionin | In Swedish = M | Metiyonin | In Turkish = M | Метіонін | In Ukrainian = M | 蛋氨酸 | In Chinese |
In English | → Biochemistry, biophysics |
| M&C | Maintenance and Checkout | In English | → Maintenance and logistics → Engineering, technology |
| M&F | Manufacturing and Facilities | In English | → Maintenance and logistics → Engineering, technology |
| M&L | Maintenance and Logistics | In English | → Maintenance and logistics → Engineering, technology |
| M&M | Materials and Maintenance | In English | → Maintenance and logistics → Engineering, technology |
| M&O | Maintenance and Operations | In English | → Maintenance and logistics → Engineering, technology |
| M&P | Moon and Planets | In English | → Serial publications, periodicals → Planets and satellites |
| M&PS | Meteoritics and Planetary Science | In English | → Serial publications, periodicals → Planets and satellites → Interplanetary medium |
| M&R | Maintenance and Refurbishment | In English | → Maintenance and logistics → Engineering, technology |
| M&R | Maintenance and Repair | In English | → Maintenance and logistics → Engineering, technology |
| M&RF | Maintenance and Refurbishing Facility | In English | → Maintenance and logistics → Engineering, technology |
| M&S | Maintenance and Security | In English | → Maintenance and logistics |
| M&S | Mapping and Surveying | In English | |
| M/C | Miscarriage | In English | → Obstetrics → Reproductive biology |
| M3AS | Mathematical Models and Methods in Applied Sciences | In English | → Serial publications, periodicals → Mathematics → Engineering, technology |
| MA&P | Maintenance Analysis and Planning | In English | → Maintenance and logistics |
| MA&SE | Mission Analysis and System Engineering | In English | → Applied sciences, technology |
| MA&T | Manufacturing Assembly and Test | In English | → Engineering, technology |
| MA:IMI | Mainstreaming Ageing: Indicators to Monitor Implementation | In English | |
| MAA | Maximum Authorized Altitude | In English | → Aeronautics, aircraft |
| MAA | Mathematical Association Of America (www.maa.org) | In English | → Associations → Mathematics |
| MAA | Marketing Authorization Application | In English | → Pharmacology, toxicology |
| MAA | Michigan Assessors Association (www.maa-usa.org) | In English | → Associations → 332 |
| MAA | Municipal Assessment Agency (www.maa.nf.ca) | In English | → Associations → 332 |
| MAA | Medieval Academy of America | In English | → Academies → History |
| MAAB | Materials Application Advisory Board | In English | → 620 |
| MAAO | Massachusetts Association of Assessing Officers (www.maao.org) | In English | → Associations → 332 |
| MAAO | Maryland Association Assessing Officers (www.maao-md.org) | In English | → Associations → 332 |
| MAAS | Mission Area Analysis System | In English | |
| MAB | Mechanical Automation Breadboard | In English | → Mechanical engineering |
| MAB | Missile Assembly Building | In English | → Military engineering |
| MAB | Master Acquisition Bus | In English | |
| MAB | Materials Applications Board | In English | → 620 |
| MAB | Materials Advisory Board | In English | → 620 |
| MAB | Monoclonal Antibody | In English | → Biochemistry, biophysics |
| MAB | Mozilla Amazon Browser | In English | → Software |
| MAC | Material Air Command | In English | |
| MAC | Mean Aerodynamic Chord | In English | → Aerodynamics |
| MAC | Maximum Allowable Concentration | In English | |
| MAC | Military Airlift Command | In English | → Military engineering → Aeronautics, aircraft |
| MAC | Multiaccess Computer | In English | → Hardware |
| MAC | Multimission Applications Concept | In English | |
| MAC | Maintenance Advisory Committee | In English | → Maintenance and logistics |
| MAC | Marginal Abatement Cost | In English | → Prices |
| MAC | Media Access Control | In English | → Networks, communication → Telecommunications |
| MAC | Media Access Controller | In English | → Telecommunications |
| MACASBE | Macau Association of Business Ethics | In English | → Associations → Ethics |
| MACDS | Monitor And Control Display System | In English | → Human-computer interaction |
| MACE | Mechanical Antenna Control Electronics | In English | → Electronics |
| MACE | Missile And Control Equipment | In English | → Military engineering |
| MACO | Major Assembly Checkout | In English | → Engineering, technology |
| MaCom | Mathematics of Computation | In English | → Computer science → Serial publications, periodicals → Mathematics |
| MACRO | Merge And Correlate Recorded Output | In English | → Data → 00592 |
| MACS | Management And Control System | In English | → Management |
| MACS | Modular Attitude Control System | In English | |
| MACSI | Mathematics, Computing and Simulation for Industry | In English | → Mathematics → Computer science → Computer simulation |
| MACVNR | Mexican Association for Computer Vision, Neurocomputing and Robotics | In English | → Associations → Computer-based techniques → Artificial intelligence → Applied sciences, technology |
| MAD | Maintenance Analysis Data | In English | → 00592 → Maintenance and logistics |
| MAD | Momentum Accumulation and Dumping | In English | |
| MADC | Multiplexer Analog-To-Digital Converter | In English | → Hardware |
| MADCS | Modular Attitude Determination and Control System | In English | → Spaceflight engineering, astronautics |
| MaDes | Machine Design | In English | → Serial publications, periodicals → Mechanical engineering |
| MadOb | Madras Observatory Observations | In English | → Serial publications, periodicals → Astronomy |
| MadOO | Madras Observatory Astronomical Observations | In English | → Serial publications, periodicals → Astronomy |
| MADRE | Manufacturing Data Retrieval | In English | → Data → Engineering, technology |
| MADS | Modular Auxiliary Data System | In English | → Data |
| MAEP | Minimum Autoland Entry Point | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| MAF | Manpower Authorization File | In English | |
| MAF | Main Assembly Fixture | In English | |
| MAF | Michoud Assembly Facility | In English | |
| MAF | Mixed Amine Fuel | In English | → Vehicle engineering |
| MAFF | Ministry of Agriculture, Food and Fisheries | In English | → Central administration → Agricultural sciences → Fishing, hunting → Food technology |
| MaFi | Mathematical Finance | In English | → Serial publications, periodicals → Mathematics → Finance |
| MAG | Modern Approaches in Geophysics | In English | → Serial publications, periodicals → Geophysics |
| MagFE | Magnetic Fusion Energy | In English | → Serial publications, periodicals → 539 |
| MAGSAT | Magnetometer Satellite | In English | → Spaceflight engineering, astronautics → Physics → Earth sciences |
| MAI | Machine-Aided Indexing | In English | → Knowledge management → Libraries |
| MAI | Monash Asia Institute | In English | |
| MAICO | Manufacturing, Assembly, Installation, and Checkout | In English | |
| MAID | Massive Array of Idle Disks | In English | → Hardware |
| MAIDS | Management Automated Information Display System | In English | → Human-computer interaction → Management |
| MAIDS | Multipurpose Automatic Inspection and Diagnostic System | In English | |
| MAIF | Maryland Automobile Insurance Fund | In English | → Insurance → Automobile manufacturing |
| MAIF | Martial Arts International Federation | In English | → Organizations and associations → Sport, physical exercises |
| Mockup And Integration Laboratory | In English | → Research institutes → Mechanical engineering |
|
| MAIR | Manufacturing And Inspection Record | In English | |
| MAL | Material Allowance List | In English | |
| MAL | Model Assembly List | In English | → Engineering, technology |
| MAL | Mobile Airlock | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| MALC | Metal Articles Liaison Committee | In English | → Organizations and associations → Metallurgy |
| MALT | Model Assembly List Transmittal | In English | → Engineering, technology |
| MAM | Media Asset Management | In English | → Computer-based techniques → Knowledge management |
| MAMP | My Arbitrary Precision Math (Library) | In English | → Software → Mathematics |
| MAN | Microwave Aerospace Navigation | In English | → Aeronautics, aircraft → Spaceflight engineering, astronautics |
| MANTECH | Manufacturing Technology | In English | → Engineering, technology |
| MAOT | Maximum Allowable Operating Time | In English | |
| MAP | Missed Approach Point | In English | |
| MAP | Maintenance Analysis Program | In English | → Maintenance and logistics |
| MAP | Measurement Allocation Plan | In English | |
| MAP | Message Acceptance Pulse | In English | |
| MAP | Mission Application Program | In English | |
| MAP | Meteorology and Atmospheric Physics | In English | → Serial publications, periodicals → Meteorology, climatology |
| MAP | Multiple Antigenic Peptide | In English | → Biochemistry, biophysics → Immunology and allergy |
| MAP | Multi-Analyte Profiling | In English | |
| MAP | Manufacturing Automation Protocol | In English | → Engineering, technology |
| MAP | Medieval Association of the Pacific | In English | → Associations → History |
| MAPC | Multipotent Adult Progenitor Cell | In English | → 5763 |
| MAPCM | Molecular Alloys Phase Change Material | In English | → Chemical technology |
| MAPEC | Multimedia Applications in Education Conference | In English | → Education → Telecommunications |
| MaPhS | Mathematical Physics Studies | In English | → Serial publications, periodicals → Mathematics → Physics |
| MAPK | Mitogen-Activated Protein Kinase | In English | → Enzymes |
| MAPOLE | Magnetic Dipole Spark Transmitter | In English | |
| MaPr | Mathematical Proceedings | In English | → Serial publications, periodicals → Mathematics |
| MAPS | Measurement of Air Pollution from Satellites | In English | → Nature → Meteorology, climatology → Spaceflight engineering, astronautics |
| MAPS-C | Master of Advanced Psychological Studies – Clinical | In English | |
| MAPTIS | Materials and Processes Technical Information System | In English | → Maintenance and logistics |
| MAR | Memory Address Register | In English | → Memories |
| MAR | Maintenance And Refurbishment | In English | → Maintenance and logistics |
| MAR | Mid-Deck Accommodations Rack | In English | |
| MARAAS | Mid-Atlantic Region Association for Asian Studies | In English | → Associations → Area studies |
| MARAD | Maritime Administration (www.marad.dot.gov) | In English | → Central administration → 6295 → Transport and postal services |
| MaRBu | Materials Research Bulletin | In English | → Serial publications, periodicals → 620 |
| MARC | Machine Readible Cataloging | In English | → Libraries |
| MARC | Modern Asia Research Centre | In English | → Area studies |
| MARC | Multiple Artificial Retina Chipset | In English | → Medicine → Electronics |
| MarGe | Marine Geodesy | In English | → Serial publications, periodicals → Geodesy, cartography → Earth sciences |
| MarGR | Marine Geophysical Researches | In English | → Serial publications, periodicals → Geophysics → Marine research, oceanography |
| MARLC | Melbourne Asian Research Libraries Consortium | In English | → Libraries → Area studies |
| MARNIS | Maritime Navigation and Information Services | In English | → Marine research, oceanography → Transport and postal services |
| MARP | Markov Analysis and Reliability Prediction | In English | → Mathematics |
| MARRS | Mission Analysis and Reconfiguration Requirements System | In English | |
| MARS | Martin Automatic Reporting System | In English | → 00592 |