Are the terms “information organization” (IO), “organization of information” (OI) and “information architecture” (IA) synonyms for knowledge organization (KO)? This study use bibliometric methods, among others, to determine some relations between these terms and their meanings. Apparently the data shows that these terms should not be considered synonyms because each of the terms IO, OI, IA and KO produce a different set of high ranked authors, journals and papers. In many cases the terms are, however, used interchangeably (and thus indicating synonymity) and it is argued that the underlying theoretical principles are identical but that the different terms has a tendency to be applied in different context: KO in the library context; IA in the web-context and IO and OI in more unspecified ways.