NASA Policy Directive 
NAPA DISCONTINUED 
NASA Program Directive 
North Polar Distance 
NASA Program Directives 
Network Probe Daemon 
Network Protection Device 
neutron powder diffraction 
neutron powder diffractometer 
New Product Development 
nitrogen phosphorus detector 
Noise Power Density 
Nominal Percent Defective 
Normal Photoelectron Diffraction 
Nuclear power development 
Numbering Plan Digit 
naive pooled data 
Nampa Police Department 
Nantucket Police Department 
Naperville Police Department 
Naples Police Department 
Napoleon Police Department 
narcissistic personality disorder 
Narcissistic Personality Disorder's 
nasal potential difference 
Nashua Police Department 
Nashville Police Department 
nasopalatine duct 
Natchez Police Department 
Natchitoches Police Department