FreeThesaurus.net takes advantage of Grady Ward's Moby Thesaurus (database), which contains a total of over 2.5 million synonyms and related terms, and is presumably the largest and most comprehensive English thesaurus data source publicly available to date.
However it is not without its errors and omissions. We do frequent updates to reflect the most recent improvements to this thesaurus database. If you spot an error in an entry, feel something is omitted, or like to see a new entry in the database soon, please do not hesitate to help us improve.
Our ajax dictionary database is based on Princeton University's WordNet project.
To Grady Ward, who compiled Moby Thesaurus back in the day on his Macintosh IIfx (68020 processor at 40 MHz, 8 MB RAM, 80 MB hard drive). Imagine FreeThesaurus.net without this awesome database.
To Dagon Design, for his really handy form mailer script that powers our feedback page.