The WordWeb English dictionary and thesaurus: fast searching, spelling suggestions, definitions, usage examples, synonyms, related words - and no adverts.
The intelligent word entry suggests possible correct spellings as you type, as well as listing words that sound the same or are often confused.
A version with 70,000 professionally recorded audio pronunciations is available as a separate product.
Additional features include the ability to drill down on any word in a definition, full bookmark support and history.
An offline audio version is available separately.
No Internet connection is required to use WordWeb, and it's free.
Chambers dictionary and thesaurus are also available, and you can cross-reference to both Chambers and old Oxford dictionary apps from WordWeb.