Na

NA, N.A., Na, nA or n/a may refer to:

Chemistry and physics

Sodium, symbol Na, a chemical element
Avogadro constant (N_A)
Nucleophilic addition, a type of reaction in organic chemistry
Numerical aperture, a number that characterizes a range of angles in an optical system
nA, the symbol for nanoampere
Naturally aspirated engine

Na (tree) or Mesua ferrea, a species of tree native to Sri Lanka
Neuroacanthocytosis, a neurological condition
Nomina Anatomica, a former international standard for human anatomical nomenclature
Noradrenaline, a hormone
Nucleic acid analogue, compounds analogous to naturally occurring RNA and DNA

Netherlands Antilles (former international vehicle registration code: NA)
Na (Chinese state), a small state of the Chinese Zhou dynasty from the 11th to 8th centuries BC
Nakoku, or Na, a state in Kyūshū, Japan from the 1st to early 3rd centuries AD

Narcotics Anonymous (NA), a twelve-step program that focuses on recovery from drug addiction
National Alliance (Latvia), a Latvian political party
National Alliance (Netherlands), a former Dutch political party
National Association (disambiguation)
National Association of Professional Base Ball Players, the first professional baseball league
Nepali Army, the land military force of Nepal
Neurotics Anonymous (N/A), a program for recovery from mental and emotional illness

.na, the top-level domain for Namibia
N/A, meaning not applicable, not available, or no answer
N.A., the official designation of federally chartered banks in the United States
Mosuo or Na, an ethnic group in China near Tibet
Na people, an ethnic group in India
National Archives, the archives of a country