| Acronym | Meaning |
| NIRNS | National Institute For Research In Nuclear Science |
| NIST | National Institute Of Standards And Technology |
| NIU | Network Interface Unit |
| NLDN | National Lightning Detection Network |
| NLDS | National Lightning Detection System |
| NLDS | National Lightning Detection System |
| NLN | NCAR Local Network |
| NLTE | Non Local Thermodynamic Equilibrium |
| NM | Network Management |
| NMC | National Meteorological Center |
| NMCC | NASCOM Management Control Center |
| NMD | NASA Master Directory |
| NMF | Normal Mode Functions |
| NMFS | National Marine Fisheries Service |
| NMHC | Non-Methane Hydrocarbons |
| NMIMT | New Mexico Institute Of Mining & Technology |
| NMOS | Network And Mission Operations Support |
| NNF | Non-NSF Funded |
| NNMI | Nonlinear Normal Mode Initialization Software |
| NNSC | NSF Net Service Center |
| NNT | Nearest Neighbor Tool |
| NOAA | National Oceanic And Atmospheric Administration |
| NOAANET | NOAA Network |
| NOAASIS | NOAA Satellite Information System |
| NOAH | Comprised Of The National Centers For Environmental Protection |
| NOAO | National Optical Astronomy Observatories |
| NOARL | Naval Oceanographic And Atmospheric Research Laboratory |
| NOC | Naval Oceanographic Command |
| NOC | Network Operations Center |
| NODC | National Oceanographic Data Center |
| NODS | NASA Ocean Data System |
| NOGAPS | U.S. Navy Operational Global Atmospheric Prediction System |
| NOHRSC | National Operational Hydrologic Remote Sensing Center |
| NOIC | National Oceanographic Instrumentation Center |
| NOMAD | Navy Oceanographic Meteorological Device |
| NOMHICE | Nonmethane Hydrocarbon Intercomparison Experiment |
| NOMP | Navy Ocean Modeling And Prediction Program |
| NOMSS | National Operational Meteorological Satellite System |
| NOPS | Nimbus Observations Processing System |
| NORDA | Naval Ocean Research & Development Activity |
| NORPAX | North Pacific Experiment |
| NOS | National Ocean Service |
| NOSC | Naval Ocean Systems Center |
| NOSIE | NODC Ocean Science Information Exchange |
| NOSS | National Ocean Satellite System |
| NOVAM | Navy Oceanographic Vertical Aerosol Model |
| NOWES | Northern Wetlands Study |
| NOWRAD | National Operational Weather Radar |
| NOZE | National Ozone Expedition |
| NPAS | Network Planning And Analysis System |