C18

C18 may refer to:

==Science and technology== Caldwell 18 (NGC 185), a dwarf spheroidal galaxy of the Local Group in the constellation Cassiopeia Carbon-18 (C-18 or 18C), an isotope of carbon , the molecular formula of cyclo(18)carbon C18, an octadecyl-type hydrocarbon with 18 carbon atoms, such as Fatty acids such as Stearic acid, C18H36O2 Oleic acid C18H34O2 C18 bonded silica stationary phase column, a type of reversed-phase chromatography column IEC 60320 C18, a power connector Colorectal cancer (ICD-10 code) ISO/IEC 9899:2018 standard for the programming language C, informally named C18