| Acronym | Meaning |
| LNAPL | Light Nonaqueous Phase Liquid |
| LNB | Low Nitrogen Oxide Burner |
| LNDO | Local Neglect Of Differential Overlap |
| LNG | Liquefied Natural Gas |
| LNGFR | Low-affinity Nerve Growth Factor Receptor |
| LNO | Localized Natural Orbital |
| LNO | Localized Natural Spin Orbital |
| LNRS | Laser Nonresonant Shadowgraphy |
| LNT | Liquid Nitrogen Temperature |
| LO | Localized Orbital |
| LOA | Linear Optical Amplifier |
| LOAEL | Lowest Observed Adverse Effect Level |
| LOC | Level Of Concern |
| LOCA | Loss-of-Coolant Accident |
| LOCI | Luminescence Oxygen Channeling Immunoassay |
| LOCOS | Local Oxidation Of Silicon |
| LOCV | Lowest-order Constrained Variation |
| LOD | Limit Of Detection |
| LOD | Loss On Drying |
| LOEC | Lowest Observed Effect Concentration |
| LOEL | Lowest-Observed-Effect Level |
| LOES | Laser Optical Emission Spectroscopy |
| LOESS | Locally Weighted Smoothers [in Modeling] |
| LOF | Lack Of Fit |
| LOGD | Limit Of Guaranteed Detection |
| LOGMO | Lowest Occupied Gaussian Molecular Orbital |
| LOGS | Laser Optogalvanic Spectrometry |
| LOH | Loss Of Heterozygosity |
| LOI | Limiting Oxygen Index [of Fire Retardant] |
| LOI | Loss Of Imprinting |
| LOI | Loss On Ignition |
| LOICZ | Land-Ocean Interactions In The Coastal Zone |
| LOIS | Land-Ocean Interaction Study |
| LOIS | Loss Of Interim Status |
| LOM | Laminated Object Manufacturing |
| LOMI | Low Oxidation-state Metal Ions |
| LOMO | Lowest Occupied Molecular Orbital |
| LOMU | Mantle Component With Low Pb-206/Pb-204 |
| LONEOS | Lowell Observatory Near-Earth-Object Search |
| LOPAC | Library Of Pharmacologically Active Compounds |
| LOPAIR | Long Path Infrared |
| LOPAP | Library Of Pharmacologically Active Peptides |
| LOPAP | Lonomia Obliqua Prothrombin Activator Protease |
| LOPC | Laser Optical Particle Counter |
| LOPT | Large-order Perturbation Theory |
| LOPT | Lowest-order Perturbation Theory |
| LOQ | Limit Of Quantitation |
| LORG | Localized Orbital-local Origin |
| LOSC | Law Of The Sea Convention |
| LOSIS | Law Of The Sea Information System |