N is the fourteenth letter of the Latin alphabet. N or n may also refer to: Mathematics , the set of natural numbers N, the field norm N for nullae, a rare Roman numeral for zero n, the size of a statistical sample Science N for Newton (unit), the SI derived unit of force N or , a normal force in mechanics Nitrogen, symbol N, a chemical element N or Asn, the symbol for the common natural amino acid asparagine N, the Normality (chemistry) or chemical concentration of a solution N, the neutron number, the number of neutrons in a nuclide N, in Brillouin zone, the center of a face of a body-centered cubic lattice n, for nano-, prefix in the SI system of units denoting a factor of 10−9 n, the optical refractive index of a material n, the principal quantum number, the first of a set of quantum numbers of an atomic orbital n, an electron density, the measure of the probability of an electron being present at a specific location n, an amount of substance in chemical physics n, the coordination number of a substance n-, a lowercase prefix in chemistry denoting the straight-chain form of an open-chain compound in contrast to its branched isomer N-, an uppercase prefix in chemistry denoting that the substituent is bonded to the nitrogen, as in amines ATC code N Nervous system, a section of the Anatomical Therapeutic Chemical Classification System Haplogroup N (mtDNA), a human mitochondrial DNA haplogroup Haplogroup N (Y-DNA), a human Y-chromosome DNA haplogroup N band, an atmospheric transmission window in the mid-infrared centred on 10 micrometres N ray, a hypothesized form of radiation, found to be illusory N., abbreviation of the Latin word nervus meaning nerve, used in anatomy, e.g. N. vagus Engineering N, in geotechnical engineering, the result of a standard penetration test N, in electrical systems, the connection to neutral N, an ITU prefix allocated to the United States for radio and television stations n (Poland), a digital TV platform N battery or N cell, a standard size of dry cell battery N connector, a threaded RF connector for joining coaxial cables Entertainment N. (novella), a 2008 short story by Stephen King Near (Death Note) (alias N), a character in the manga series Death Note N (video game), a 2005 computer game N (Pokémon), the leader and king of crime syndicate Team Plasma in the