WordNet Domains is a lexical resource created in a semi-automatic way by augmenting WordNet with domain labels. WordNet Synsets have been annotated with at least one semantic domain label, selected from a set of about two hundred labels structured hierarchically. Information brought by domains is complementary to what is already in Wordnet. A domain may include synsets of different syntactic categories and from different WordNet sub-hierarchies. Domains may group senses of the same word into homogeneous clusters, with the side effect of reducing word polysemy in WordNet.