The main source of TheFreeDictionary's general English dictionary is Houghton Mifflin's premier dictionary, the American Heritage® Dictionary of the English Language, Fourth Edition. This authoritative work is the largest of the American Heritage® dictionaries and contains over 200,000 boldface terms and more than 33,000 written examples. The Fourth Edition also incorporates more than 10,000 new words.

Containing 260,000 entries, the general dictionary is augmented with Collins English Dictionary – Complete and Unabridged, and is enhanced by 30,000 illustrations, an audio pronunciation feature, etymologies, abbreviations, biographical entries, and more. Definitions are accompanied by usage examples from classic works of literature, courtesy of The Free Library.

Additionally, translations to Spanish, French, German, and Italian are provided by HarperCollins and feature contemporary vocabulary and expressions—including everyday terms relating to business, computing, current events, tourism and many other topics.