As promised in an earlier post, I'm going to have a look at some iPhone/iPod Touch apps which would be useful for learners of English. First of all, English<>English dictionaries. If you've got a limited budget (or no budget at all), four stand out from the dozens available on the App Store:
• Dictionary.com: free dictionary and thesaurus including nearly 1,000,000 words & definitions and 90,000 synonyms and antonyms. No Internet connection is needed. The app also features audio pronunciations, similarly spelled words and Dictionary.com's popular Word of the Day.
• WordBook English Dictionary & Thesaurus: comparable to the Dictionary.com app with one major advantage—all the words in the definitions are linked to their own definitions. Also gives word origins. Not free, but $1.99 is a small price to pay for such an excellent product.
• Dictionary?: Free, easy-to-use, comprehensive international English dictionary and thesaurus. Fast searching, detailed definitions, synonyms, derived words, examples, and hyperlinked entries. An original feature is the cross-referencing with online sources such as Wikipedia and Answers.com. An audio version with with 70 000 professionally recorded pronunciations is available for $4.99.
• Advanced English Dictionary and Thesaurus: The WordNet Dictionary and Thesaurus is a large lexical database of English with up to 140,000 entries and more than 1.4 million words, developed by the Computer Science Department at Princeton University. Hyperlinked entries with antonyms, hypernyms and hyponyms (look them up!) It's free, so you may as well install it and make your own mind up.
If money's no object, you might be tempted by one of the Big Three: The Oxford English Dictionary, Merriam-Webster, and American Heritage. But that will set you back anything between $19.99 and $59.99 (!). MacWorld has a detailed review of these.
To finish, I should also mention Slango, which is the app version of the wonderful Urban Dictionary. If you want to know what a stoplight party is, this is the place to look. The Slango app is only $0.99, so you'd have to be a real cheapskate not to download it.