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. Synsets are interlinked by means of conceptual-semantic
and lexical relations. The resulting network of meaningfully related words
and concepts can be navigated with the browser. WordNet is also freely
and publicly available for download.  WordNet's structure makes it a
useful tool for computational linguistics and natural language processing.