Oxford University Press will this year release a book that has taken almost 45 years to finish. It’s the world’s largest thesaurus — and includes almost the entire vocabulary of English. The project was begun in 1965.

A spokesman said the final tome would contain over 230,000 categories with 800,000 meanings. The thesaurus was nearly completed in 1980, but the team decided to include words from updated versions of the Oxford English Dictionary. This added almost 30 years more work to the project.