| Acronym | Meaning |
| NODS | NASA Ocean Data System |
| NOE | Nuclear Overhauser Effect (NMR) |
| NOE | Nuclear Overhauser Enhancement |
| NOEC | No Observed Effect Concentration |
| NOEL | No Observable Effect Level (in Animal Tests) |
| NOES | National Occupational Exposures Survey |
| NOESY | Nuclear Overhauser Effect Spectrometry |
| NOET | NASA Operational Environment Team |
| NOGF | Nonorthogonal Group Function Approximation |
| NOHS | National Occupational Hazard Survey |
| NOHSC | National Occupational Health And Safety Commission (Australia) |
| NOI | Notice Of Intent |
| NOLMOS | Nonorthogonal (strictly) Local Molecular Orbitals |
| NOM | Natural Organic Matter |
| NOMAD | Neutrino Oscillation MAgnetic Detector |
| NOMS | National Organics Monitoring Survey (US EPA 1976-1977) |
| NOONS | Natural Orbitals Occupation Numbers |
| NOPES | Nonoccupational Pesticide Exposure Study |
| NORA | National Occupational Research Agenda |
| NORM | Naturally Occurring Radioactive Material(s) |
| NORS | National Organics Reconnaissance Survey (US EPA 1974-1975) |
| NOS | Nitric Oxide Synthase |
| NOS | Not Otherwise Specified |
| NOSC | Naval Ocean Systems Center |
| NOV | Notice Of Violation |
| NOW | Nonhazardous Oil Field Waste |
| NOX | Nitrogen Oxides |
| NPA | Natural Population Analysis |
| NPA | Natural Population Analysis (for Electron Configuration Of Mols.) |
| NPAH | Nitro-polycyclic Aromatic Hydrocarbon |
| NPAPS | Non-phase Alternation Pulse Sequence |
| NPAR | Nonbinding Preliminary Allocation Of Responsibility |
| NPC | Niemann-Pick Type C Disease |
| NPC | Nasopharyngeal Carcinoma |
| NPC | Nonparenchymal Cell |
| NPC | Nuclear Pore Complex |
| NPCA | National Paint And Coatings Association (US) |
| NPCR | Nonlinear Principal Components Regression |
| NPCVD | Normal Pressure Chemical Vapor Deposition |
| NPD | Nitrogen Phosphorus Detector (gas Chromatography) |
| NPD | Normal Photoelectron Diffraction |
| NPDES | National Pollutant Discharge Elimination System |
| NPDOC | Non-purgeable Dissolved Organic Carbon |
| NPDWR | National Primary Drinking Water Regulations |
| NPIRS | National Pesticide Information Retrieval System |
| NPL | National Physical Laboratory |
| NPL | National Priorities List |
| NPL | Nonparametric Linkage |
| NPL | Nuclear-pumped Laser |
| NPM | Nonpolar Material |