The Basque WordNet is a lexical database including information about Basque words. It is an extension of WordNet 1.6, a lexical database for English developed at the Princeton University. The Basque WordNet is tightly aligned to the English WordNet. The Basque WordNet models nouns, verbs and adjectives. Each sense is linked to a so-called synset. Every synset encodes the synonymy relation between (possibly) several words (synonyms), having a unique meaning, belonging to one and the same part of speech (specified in the POS tag value), and expressing the same lexical meaning. Each synset is related to the corresponding synset in the English WordNet 1.6. via its identification number ID, which includes the synset number and the POS tag. The only exceptions are newly created synsets to account for cultural concepts not present in WordNet 1.6. The Basque WordNet is provided following the Lexical Markup Framework (LMF, ISO/TC37) and it contains the following: • set of variants or synonyms making up the synset; • part-of-speech; • language-internal relations to other synsets; • a unique-id linking the Basque synsets to the English Wordnet 1.6; • glosses and examples for a subset of the synsets • mappings to WordNet domains, Sumo and Basic Concepts LMF can be imported directly in the DebVisDic tool for browsing and editing wordnets (not included). Figures for the Basque WordNet are distributed as follows : - 30,281 Synsets: 26,708 nouns, 3,455 verbs, 118 adjectives - 49,688 Variants: 40,042 nouns, 9,491 verbs, 155 adjectives - 26,727 Lemma + pos: 23,176 nouns, 3,494 verbs, 57 adjectives - 1.66 Synonym per synset: 1.52 nouns, 2.74 verbs, 1.21 adjectives - 1.86 Senses per lemma+pos: 1.73 nouns, 2.72 verbs, 2.72 adjectives - 94,482 InternalRelations: 74,857 nouns, 19,492 verbs, 133 adjectives - 2,323 Definitions (nouns only) - 35,346 WordNet Domains mappings: 31,631 nouns, 3,590 verbs, 125 adjectives - 30,018 Sumo mappings: 26,446 nouns, 3,454 verbs, 118 adjectives - 1,138 Basic Concepts: 740 nouns, 398 verbs