 Farlex also maintains a companion title, The Free Library, an online library of out-of-copyright classic books and a collection of periodicals of over four million articles dating back to 1984, and definition-of.com, a community dictionary of slang and other terms.Wikipedia content is hosted at the sub-domain encyclopedia.thefreedictionary.com, which is excluded from search-engine indexing in its entirety by Farlex with the use of meta tags.This is done to avoid duplicate content in the search-engine results and prevent user traffic that would otherwise go to Wikipedia.