WordNet is lexical ontology for English language. It models the lexical Knowledge into a taxonomic hierarchy. WordNet contains three databases one for nouns, one for verbs and one for adverb and adjectives. Terms and concepts are organized into synsets (list of synonyms terms or concepts). We have considered only is-a relationship and noun concepts in the WordNet hierarchy for similarity calculation.
We use WordNet 3.1, which contains nine separate noun hierarchies containing, path between two concepts may not exists in the WordNet. Therefore, we create a root node that subsumes all the nine given hierarchies in the WordNet.