cyano group, in chemistry, functional group that consists of a carbon atom joined to a nitrogen atom by a triple bond; it can be joined to an atom or another group by a single bond to the carbon atom. When a cyano group is joined to hydrogen, it forms hydrogen cyanide. When it is joined to a metal, it forms a metal cyanide. When it is joined to an alkyl group or aryl group, it forms a nitrile. When two cyano groups are joined directly to one another, they form the cyanogen molecule, NCCN. Both the cyano group and hydrogen cyanide have been found in interstellar space.