nEnglishOxford Dictionary of Englishn /ɛn / ▸ abbreviation [in combination] 1 (in units of measurement) nano- (10−9): 500 ng. 2 Grammar neuter. 3 [in combination] Chemistry (n-) normal (denoting straight-chain hydrocarbons): n-hexane. 4 note (used in a book's index to refer to a footnote): 450n. 5 Grammar noun. ▸ symbol an unspecified or variable number. See also nth:at the limit where n equals infinity.