NACE (National Association of Corrosion Engineers)
NAFTA (North American Free Trade Agreement)
Naphthene (CnH2n, or Cycloalkane)
National Centres for Environmental Information (NCEI)
National Geodetic Vertical Datum (NGVD)
National Human Genome Research Institute (NHGRI)
National Ignition Facility (NIF)
National Oceanic and Atmospheric Administration (NOAA)
National Regulatory Authorities (NRAs)
National Rural Electric Cooperative Association (NRECA)
Natural Gas Combined Cycle (NGCC)
Natural Gas Steam Reforming Production
NCI (National Cancer Institute)
NCND (Non Circumvention Non Disclosure)
NDA (Non Disclosure Agreement)
NDA (Nuclear Decommissioning Authority)
NDE (Non-Destructive Examination)
NEI (Nuclear Energy Institute)
NEMA (National Electrical Manufacturers Association)
Nephelometric Turbidity Unit (NTU)
Net (Lower) Heating Value (NHV)
Net Energy Production (or Balance)
Net Positive Suction Head (NPSH)
Netback from Final Product (NET)
Neutralisation (Neutralization)
Neutron Radiographic Testing (NR)
Newton's Law of Universal Gravitation
NFPA (National Fire Protection Association)
NFPA (National Fire Protection Association) 55
NFPA 70: NEC (National Electric Code)
NGO (Non-Governmental Organisation)
NGSA (Natural Gas Supply Association)
NIA (Nuclear Industry Association) UK
NIST (National Institute of Standards and Technology)
Nitrogenous Oxygen Demand (NOD)
No Tillage (also Zero Tillage)
Non Associated Gas (or Nonassociated Gas)
Non Cultivated Biological Resource
Non-random Sampling (or Non-probability Sampling)
North American Charging Standard (NACS)
Nuclear Magnetic Resonance (NMR)
Nuclear Power Plant (NPP) or Nuclear Power Station
Nuclear Regulatory Commission (NRC)