Much effort has been spent on the construction of Korean language resources for Korean language processing. KOLON was one of these works. It created a unified lexicon for Korean by mapping Korean words onto Mikrokosmos concepts and combining the result with information from the Sejong Dictionary. The lexicon can obtain syntactic and semantic constraints on the argument structures of a word through inheritance of constraints originating from the conceptual structure. Currently KOLON contains 65,326 word senses collected from nouns, verbs and adjectives. Synonyms link to a single concept and cover a wide range of words. We can reclassify synonyms into small subgroups by putting syntactic and semantic constraints on their argument structures. These classifications can be a good resource for Korean language education as well as for Korean language processing.