WordNet Lexical Database
Large lexical database with ~117,000 synsets linked by semantic and lexical relations. Foundation of computational linguistics.
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Where this one tends to earn its keep.
Word sense disambiguation in NLP
Machine translation lexical resources
Text classification feature enrichment
Building domain-specific lexicons
I haven't checked this label against the actual licence text — it's the catalogue's original guess. Check the ontology's own site before you rely on it.
Others worth a look in Knowledge Graphs.