| L5 | Last 5 |
| LA | Los Angeles (USA) |
| LA | Long Acting |
| LAA | Left Atrial Appendage |
| LAAC | Left Atrial Appendage Closure |
| LAAM | LAA Man. |
| LAB | Linear Alkyl Benzene |
| LABA | Long Acting Beta Agonist |
| LABS | Linear Alkyl Benzene Sulfonate |
| LACI | Lipoprotein Associated Coagulation Inhibitor |
| LADI | Laser-Assisted Direct Imprint |
| LAG | Lymphocyte Activation Gene |
| LAH | Lithium Aluminum Hydride |
| LAI | Long-Acting Injectable |
| LAIV | Live-Attenuated Influenza Vaccine |
| LALLS | Low Angle Laser Light Scattering |
| LAMA | Long Acting Muscarinic Antagonist |
| LAMP | Limbic - System Associated Membrane Protein |
| LAMP | Lysosome-Associated Membrane Protein |
| LAN | Local Area Networks |
| LAO | Linear Alpha Olefins |
| LAP | Lipoxygenase Activating Protein |
| LAP Cardio | Left Atrial Pressure |
| LAR | Long Acting Release |
| LAS | Linear Alkylbenzene Sulfonate |
| LAS | Lymph Adenopathy Syndrome |
| LAT | Lysine Amino Transferase |
| LATV | LATVia |
| LB | LeBanon |
| LBCL | Large B-Cell Lymphoma |
| LBD | Ligand Binding Domain |
| LBD | Ligand Binding Domain |
| LBL | Layer-By-Layer (assembly technique) |
| LBL Onco. | LymphoBlastic Lymphoma |
| LBP | Lipopolysaccharide Binding Protein |
| LBS | Location-Based Service |
| LC | Liquid Chromatography |
| LC | Liquid Crystal |
| LCA | Life Cycle Assessment |
| LCA | Life Cycle Analysis |
| LCAT | Lecithin Cholesterol Acyl Transferase |
| LCB-SVA | Long Chain Branched - Syndiotactic Vinyl Aromatic |
| LCD | Liquid Crystal Display |
| LCF | Lymphocyte Chemoattractant Factor |
| LCM | Life Cycle Management (Pharma.) |
| LCM | Laser Capture Microdissection |
| LCNMR | Liquid Chromatography Nuclear Magnetic Resonance |
| LCP | Liquid Crystal Polymer |
| LCP | Liquid Crystal Poly(Ester) |
| LCST | Lower Critical Solution Temperature |
| LCT | Long Chain Triglyceride |
| LCTE | Linear Coefficient of Thermal Expansion |
| LCV | light commercial vehicles |
| LDA | Lithium Diisopropyl Amide |
| LDGF | Leukocyte Derived Growth Factor |
| LDH | Lactate De Hydrogenase |
| LDL | Low Density Lipoprotein |
| LDP | Large Distal Platform |
| LDPE | Low Density Poly(ethylene) |
| LDR | Low Dropout Regulators |
| LDS | Li Di Silicate |
| LDV | Lipid Deposition Value |
| LDW | Lane Departure Warning |
| LE | Lotus Effect |
| LE Eye | Loteprednol Etabonate |
| LED | Light Emitting Diode |
| LEED | Leadership in Energy & Environmental Design |
| LEMS | Lambert Eaton Myasthenic Syndrome |
| LEO | low earth orbiting |
| LEP | Light Emitting Polymer |
| LES | Layered Expression Scanning |
| LESA | Liquid Extraction Surface Analysis |
| LFA | Lymphocyte Functioning Associated (antigen) |
| LFI | Lateral Flow Immunoassay |
| LFP | Linear Field Planar |
| LFP | Li Fe Phosphate |
| LFRT | Long Fiber Reinforced Thermoplastic |
| LFS | Li Fraumeni Syndrome |
| LFS | Leukemia Free Survival |
| LGL | Large Granular Lymphocyte |
| LGS | Layered Gene Scanning |
| LGS | Lennox Gastaut Syndrome |
| LH | Luteinizing Hormone |
| LHA | Lower Halogenated Alkane |
| LHC | Large Hadron Collider |
| LHON | Lebers Hereditary Optic Neuropathy |
| LHRH | Luteinizing Hormone Release Hormone |
| LHRHa | LHRH Analogue |
| LHSV | Liquid Hourly Space Velocity |
| LIBS | Laser Induced Breakdown Spectroscopy |
| LIC | LI ion Capacitors |
| LiDAR | Light Detection And Ranging |
| LIF | Laser Induced Fluorescence |
| LIGO | Laser Interferometer Gravitational-wave Observatory |
| LIMS | Laboratory Information Management System |
| LISH | Ligation In Situ Hybridization |
| LLDPE | Linear Low Density Poly(ethylene) |
| LLE | Lipid Layer Enhancer |
| LLNL | Lawrence Livermore National Laboratory (USA) |
| LLO | Listerio Lysin O |
| LmeIF | Leish Mania braziliensis of Eukaryotic Initiation Factor |
| LMG | Liquid Metal Gasification |
| LMWH | Low Molecular Weight Heparin |
| LN2 | Liquid N2 |
| LNG | Liquefied Natural Gas |
| LNGFR | Low-affinity Nerve Growth Factor Receptor |
| LNKS | Lovastatin Nona Ketide Synthase |
| LNP | Lipid NanoParticle |
| LNVM | Logic Non-Volatile Memory |
| LO | Lipo Oxygenase |
| LoDoCo | Low Dose Colchicine |
| LOHAS | Lifestyles Of Health And Sustainability |
| LOI | Limiting Oxygen Index |
| LOI | Letter Of Intent |
| LOPD | LATE-ONSET POMPE DISEASE |
| LPA | Lyso Phospholipid Acid |
| LPA | Lyso Phosphatidic Acid |
| LPAAT | Lysophosphatidic Acid Acyl Transferase |
| LPE | Lisinopril Ethyl Ester |
| LPF | Lymphocyte Promoting Factor |
| LPF | Lymphocytosis Promoting Factor |
| LPG | Liquified Petroleum Gas |
| LPIC | Lipid Peroxidation Inhibition Capacity |
| LPL | Lipo Protein Lipase |
| LPNC | Linear Phospho Nitrile Catalyst |
| LPPS | Liquid Phase Peptide Synthesis |
| LPS | Lipo Poly Saccharide |
| LPWAN | Low Power Wide Area Network |
| LRTD | lower respiratory tract disease |
| LSC | Leukemic Stem Cell |
| LSD | Lysergic Acid Diethylamide |
| LSD | Lysosomal Storage Diseases |
| LSD | Limited Slip Differential (Automotive) |
| LSPR | Localized Surface Plasmon Resonance |
| LSR | Liquid Silicone Rubber |
| LSS | Lumbar Spinal Stenosis |
| LT | heat-Labile-entero Toxin (of E. coli) |
| LTA | Lympho Toxin Alpha (gene cardiology) |
| LTB | Leuko Triene B |
| LTB | heat-Labile-entero non-Toxic subunit B (of E. coli) |
| LTP | Long Term Potentiation (NeuroSciences) |
| LTPSi | Low Temperature Polycrystalline Si (displays) |
| LTRA | Leuko Triene Receptor Antagonist |
| LUCA | Last Universal Common Ancestor |
| LULDPE | Linear Ultra Low Density Poly Ethylene |
| LUMO | Lowest Unoccupied Molecular Orbital |
| LUTS | Lower Urinary Tract Symptoms |
| LUV | Large Unilamellar Vesicles (liposomes) |
| LV | left ventricular |
| LV Vasc. | Lumi Vascular |
| LVAS | Left Ventricular Assist System |
| LVAS Lung | Lung Ventilation Analysis Software |
| LVEF | Left Ventricular Ejection Fraction |
| LVH | Left Ventricular Hypertrophy |
| LVO | Large Vessel Occlusion |
| LVOT | Left Ventricular Outflow Tract |
| LVP | Large Volume infusion Pump |
| LVRT | Low Voltage Ride Through (Batteries) |