WordNet is a large lexical database of English, developed under the direction of George A. Miller. Nouns, verbs, adjectives and adverbs are grouped into sets of cognitive synonyms (synsets), each expressing a distinct concept.
P. Martin. Proceedings of the 11th International Conference on Conceptual Structures (ICCS 2003), Volume 2746 von Lecture Notes in Computer Science, Seite 160-173. Springer, (2003)