| N | Nano | - | Astronomy |
| N | Newton - Nitrogen - North | - | Astronomy |
| N/A | Not Available/applicable | - | Astronomy |
| N/K/A | Now Known As | - | Astronomy |
| N/T | (Aa) No Text | - | Astronomy |
| N3F | National Fantasy Fan Federation | - | Astronomy |
| NA | Namibia (ISO 3166 Digram) -National Archives - Negative Acknowledge | - | Astronomy |
| NA | Nanoampere | - | Astronomy |
| NA | Nauruan Language (ISO 639-1 Code) | - | Astronomy |
| NA | Sodium | - | Astronomy |
| NAA | N-Acetylaspartate | - | Astronomy |
| NAACP | National Association For The Advancement Of Colored People (N Double-A CP) | - | Astronomy |
| NAAD | North American Air Defense | - | Astronomy |
| NAAFI | Navy | - | Astronomy |
| NAAK | Mark I NAAK | - | Astronomy |
| NAAQS | National Ambient Air Quality Standards | - | Astronomy |
| NAAWS | NATO Anti-Air Warfare System | - | Astronomy |
| NABCI | North American Bird Conservation Initiative (nab-see) | - | Astronomy |
| NAC | National Agency Check - U.S. Naval Avionics Center - U.S. Navy Advanced Concepts - North Atlantic Council - Northern Area Command | - | Astronomy |
| NACA | (U.S.) National Advisory Committee For Aeronautics (1915?1958 | - | Astronomy |
| NACC | North Atlantic Cooperation Council | - | Astronomy |
| NACISA | NATO Communications And Information Systems Agency | - | Astronomy |
| NACMA | NATO Air Command And Control System Management Agency | - | Astronomy |
| NAD | Namibian Dollar (ISO 4217 Currency Code) | - | Astronomy |
| NAEC | U.S. Naval Air Engineering Center | - | Astronomy |
| NAF | NATO Architecture Framework -Naval Air Facility | - | Astronomy |
| NAFLD | NonAlcoholic Fatty Liver Disease | - | Astronomy |
| NAFO | Northwest Atlantic Fisheries Organization | - | Astronomy |
| NAFTA | North American Free Trade Agreement | - | Astronomy |
| NAGPRA | Native American Graves Protection And Repatriation Act | - | Astronomy |
| NAI | Named Area Of Interest -Network Access Identifier | - | Astronomy |
| NAICS | North American Industry Classification System | - | Astronomy |
| NAILS | National Airspace Integrated Logistics System | - | Astronomy |
| NAIRU | Non Accelerating Inflation Rate Of Unemployment | - | Astronomy |
| NAK | Negative Acknowledge | - | Astronomy |
| NAM | Namibia (ISO 3166 Trigram) | - | Astronomy |
| NAMBLA | North American Man-Boy Love Association | - | Astronomy |
| NAMRL | Naval Aerospace Medical Research Laboratory | - | Astronomy |
| NAN | Not A Number (computing) | - | Astronomy |
| NAO | UK National Audit Office | - | Astronomy |
| NAPDD | Non-Acquisition Program Definition Document (nap-dee-dee) | - | Astronomy |
| NAPS | Navy Acquisition Procedures Supplement | - | Astronomy |
| NARA | (U.S.) National Archives And Records Administration | - | Astronomy |
| NARAL | National Abortion Rights Action League | - | Astronomy |
| NARDAC | Naval Regional Data Automation Center | - | Astronomy |
| NARDIC | U.S. Navy Acquisition Research And Development Information Center | - | Astronomy |
| NARPV | National Association For Remotely Piloted Vehicles | - | Astronomy |
| NAS | National Academy Of Sciences - National Air Space - National Audubon Society - Naval Air Station - New Attack Submarine | - | Astronomy |
| NASA | National Aeronautics And Space Administration | - | Astronomy |
| NASCAR | National Association For Stock Car Auto Racing | - | Astronomy |
| NASDAQ | National Association Of Securities Dealers Automated Quotations (an American Stock Exchange). | - | Astronomy |
| NASED | National Association Of State Election Directors [1][2] | - | Astronomy |
| NASH | Non-Alcoholic SteatoHepatitis | - | Astronomy |
| NASP | National Aerospace Plane | - | Astronomy |
| NASS | National Association Of Secretaries Of State [3] | - | Astronomy |
| NATO | National Association Of Theatre Owners - North Atlantic Treaty Organisation | - | Astronomy |
| NAU | Nauruan Language (ISO 639-2 Code) | - | Astronomy |
| NAV | Navigation[al] | - | Astronomy |
| NAV | Navajo Language (ISO 639-2 Code) | - | Astronomy |
| NAVCAMS | Naval Communications Area Master Station | - | Astronomy |
| NAVCC | National Audio-Visual Conservation Center | - | Astronomy |
| NAVCC (NAVY) | Navy Component Commander | - | Astronomy |
| NAVCENT | Naval Forces U.S. Central Command | - | Astronomy |
| NAVEUR | Naval Forces U.S. European Command | - | Astronomy |
| NAVFE | U.S. Naval Forces | - | Astronomy |
| NAVFOR | Naval Force | - | Astronomy |
| NAVMACS | Naval Modular Automatic Communication Subsystem | - | Astronomy |
| NAVNET | Navy Network | - | Astronomy |
| NAVS | Non-Cooperative Airborne Vector Scoring | - | Astronomy |
| NAVSAT | Navigation Satellite | - | Astronomy |
| NAVSPACECOM | U.S. Navy Space Command | - | Astronomy |
| NAVSPASUR | U.S. Naval Space Surveillance System | - | Astronomy |
| NAVSTAR | Navigation Satellite Timing And Ranging | - | Astronomy |
| NAVTACNET | Navy Tactical Network | - | Astronomy |
| NAWC | U.S. Naval Air Warfare Center | - | Astronomy |
| NAWMP | North American Waterfowl Management Plan (gnaw-wump) | - | Astronomy |
| NB | New Brunswick (postal Symbol) -nota Bene (Latin | - | Astronomy |
| NB | Niobium | - | Astronomy |
| NB | Norwegian Bokm?l Language (ISO 639-1 Code) | - | Astronomy |
| NBA | National Basketball Association | - | Astronomy |
| NBACC | U.S. National Biodefense Analysis And Countermeasures Center (enn-back) | - | Astronomy |
| NBC | National Broadcasting Corporation - Nuclear | - | Astronomy |
| NBCRS | NBC (Nuclear | - | Astronomy |
| NBL | Southern Ndebele Language (ISO 639-2 Code) | - | Astronomy |
| NBT | Nitroblue Tetrazolium (assay) | - | Astronomy |
| NC | Network Computer -New Caledonia (ISO 3166 Digram) -Node Centre - Non-Consensual - Normally Closed -North Carolina (postal Symbol) | - | Astronomy |
| NC | Nanocoulomb | - | Astronomy |
| NC3A OR NC?A | NATO Consultation | - | Astronomy |
| NCA | National Command Authority | - | Astronomy |
| NCAA | National Collegiate Athletic Association (NC Double A) | - | Astronomy |
| NCAR | U.S. National Center For Atmospheric Research | - | Astronomy |
| NCB | National Codification Bureau | - | Astronomy |
| NCCAM | U.S. National Center For Complementary And Alternative Medicine | - | Astronomy |
| NCDDR | U.S. National Center For The Dissemination Of Disability Research | - | Astronomy |
| NCES | U.S. National Center For Education Statistics - Net-Centric Enterprise Services | - | Astronomy |
| NCI | U.S. National Cancer Institute | - | Astronomy |
| NCIS | National Criminal Intelligence Service (British) - Naval Criminal Investigative Service (U.S. Navy) | - | Astronomy |
| NCL | New Caledonia (ISO 3166 Trigram) | - | Astronomy |
| NCO | Non-Commissioned Officer | - | Astronomy |
| NCP | Net Contracted Purchases | - | Astronomy |
