| Acronym | Meaning |
| LACE | Lectin Affinity Capillary Electrophoresis |
| LACO | Linearized Atomic Cell Orbital (in Energy-band Calcn.) |
| LAD | Left Anterior Descending |
| LAD | Leukocyte Adhesion Deficiency |
| LADD | Lifetime Average Daily Dose |
| LADD | Lowest Acceptable Daily Dose |
| LADH | Liver Alcohol Dehydrogenase |
| LAEC | Lowest Achievable Emission Rate |
| LAER | Lowest Achievable Emission Rate |
| LAESA | Laser Ablation Emission Spectrochemical Analysis |
| LAGST | Leaking Above Ground Storage Tank |
| LAH | Lithium Aluminum Hydride |
| LAI | Leukocyte Adherence Inhibition |
| LAI | Leaf Area Index |
| LAICP | Laser Ablation Inductively Coupled Plasma |
| LAIS | Liquid Alloy Ion Source |
| LAIV | Live Attenuated Influenza Virus |
| LAK | Lymphokine Activated Killer |
| LAKE | Clean Lakes Database (accessible Through OLS) |
| LAL | Limulus Amebocyte Lysate (endotoxin Test) |
| LALA | Large Area Lyman Alpha |
| LALIF | Laser Atomization/Laser Induced Fluorescence |
| LALLS | Low Angle Laser Light Scattering |
| LAMBD | Laser Assisted Molecular Beam Deposition |
| LAMES | Laser Micro Emission Spectroscopy |
| LAMMA | Laser Microprobe Mass Analysis |
| LAMMS | Laser Micro Mass Spectrometry |
| LAMOFS-ETE | Laser Excited Molecular Fluorescence Spectroscopy With Electrothermal Evaporation |
| LAMP | Lake Acidification Mitigation Project |
| LAMP | Lysosome-Associated Membrane Protein |
| LAMP | Laser Ablation Microprobe |
| LAMPRE | Los Alamos Molten Plutonium Reactor Experiment |
| LAMS | Laser Mass Spectrometry |
| LAN | Local-area Network |
| LANL | Los Alamos National Laboratory |
| LAO | London Atomic Orbital |
| LAOCOON | Least-squares Adjustment Of Calculated On Observed NMR Spectra |
| LAOES | Laser Ablation Optical Emission Spectroscopy |
| LAOM | Localized At. Orbital Method (in Electronic Structure Calcn.) |
| LAOS | Large Amplitude Oscillatory Shear |
| LAOS | Light Amplifying Optical Switch |
| LAP | Laboratory Accreditation Program |
| LAP | Laboratory Analytical Protocol |
| LAP | Latency-associated Peptide |
| LAPIS | Linden Atmosphere/Phytosphere Interaction Study |
| LAPS | Light-Addressable Potentiometric Sensor |
| LAPW | Linearized Augmented Plane Wave (for Band-structure Calcns.) |
| LAQL | Lowest Analytically Quantifiable Level |
| LARIS | Laser Ablation And Resonance Ionization Spectroscopy |
| LART | Laser Absorption Radiation Thermometry |