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 Ampere, nanoampere * Naturally aspirated engine

Biology and medicine

* 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

Places

Current

* Namibia (ISO country code) * Naples (car number plate code: NA), Italy * North America, a continent * North Africa, a subcontinent

Historical

* 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

Names and titles

* Na (Korean surname), Na (羅), a Korean surname related to the Chinese surname Luo (surname), Luo * Na, a particle used in Thai name#Royal and noble names, Thai noble names * National Academician, a member of the National Academy of Design

Art and entertainment

* Na (drum), a drum played by Tibetan shamans * Nahal, Shine's pet Bengal tiger on the Nick Jr. TV show ''Shimmer and Shine'' * New adult fiction, fiction marketed to people 18–30 years old * ''Virgin New Adventures'', a series of ''Doctor Who'' novels * Na (EP), ''Na'' (EP) by Nayeon, 2024

Transport

* NA, the tailcode of VFA-94 * Nepal Airlines, the national flag carrier airline of Nepal * North American Airlines (IATA code: NA) * Naturally aspirated engine * Mazda MX-5 (NA), NA MX-5 Miata, the first generation of the Mazda Miata

Language

* Na (cuneiform), a cuneiform sign * Na (Javanese) (ꦤ), a letter in the Javanese script * Na (kana), a Japanese kana * Na dialect, a Sino-Tibetan variety of India * Na language (Narua), a Sino-Tibetan language of Yunnan, China * Nauruan language (ISO code: na)

Organizations

* 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

Other uses

* .na, the top-level domain for Namibia * N/A, meaning not applicable, not available, or no answer * N.A., the official designation of National bank (United States), 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, National Archives, the archives of a country