| Naval Architectural PAckage | Academic & Science |
| National Academy of Performing Arts | Academic & Science |
| National Academy of Public Administration | Academic & Science |
| National Association for the Practice of Anthropology | Academic & Science |
| National Asphalt Pavement Association | Business |
| National Acrylic Painters Association | Business |
| National Automobile Parts Association | Business |
| National Association for Providers of Activities | Community |
| National Automotive Parts Association | Community |
| National Activity Providers Association | Community |
| National APIA Panhellenic Association | Community |
| National Auto Parts Association | Community |
| North America Pool Association | Community |
| National APIDA Panhellenic Association | Community |
| National Association for Plan Advisors | Community |
| Not A Problem Anymore | Computing |
| Network Application Performance Analysis | Computing |
| Not A Pocono Achiever | General |
| Need Another Part ASAP (As Soon As Possible) | General |
| No Atlanta Petitions Accepted | General |
| Never Ask Phil Anything | General |
| No Auto Parts Available | General |
| No Artificial Preservatives Added | General |
| National Adaptation Plan of Action | General |
| National Allowance Pricing Agreement | General |
| No Appropriate Placement Available | General |
| North American Phonetic Alphabet | General |
| No Apto Para Adultos | General |
| No Apparent Professionals Anywhere | General |
| Not Any Parts Available | General |
| Never Any Parts Available | Governmental |
| National Aviation Parts Assistance | Governmental |
| North American Pedophile Association | Governmental |
| National Adaptation Programme of Action | Governmental |
| No African People Allowed | Governmental |
| No Appropriate Parts Available | Governmental |
| Neurological and Physical Abilitation Center | Medical |
| North American Partners in Anesthesia | Medical |
| National Academy of Political Awareness | Regional |