Reference apps can be highly specific—like a ship captain's medical guide, or broad—like the Encyclopedia Britannica. In this section you'll find political reference manuals, medical and legal materials, compilation of great quotations, joke databases, and much more. Whether you're a professional, a student, or just a curious person, there's an app for just about any reference material you can think of.
Advanced English Dictionary & Thesaurus ($0.99, app2.me/2891) shows how every word is linked to another. Type in the word, "tree" and you will not only get the definition, synonyms and opposites, but the hypernyms (a tree is a kind of what?), meronyms (what are the parts of a tree?) and more.
Constitution for iPhone and iPod touch (Free, app2.me/2892) Complete copy of the U.S. Constitution with notes and an index.
Dictionary.com-Dictionary & Thesaurus (Free, Paid version available, app2.me/204) Includes nearly 1,000,000 words and definitions and 90,000 synonyms and antonyms.
The World Factbook 2010 ($0.99, app2.me/2672) is a reliable source of information on all the nations of the world.
Wikipanion (Free, app2.me/2663) is designed for easy search, navigation, and display of Wikipedia entries.
WordBook English Dictionary & Thesaurus ($1.99, app2.me/2893) is a comprehensive, quick, and intuitive dictionary and thesaurus. It's a great combination of comprehensive contents and a fast intuitive interface, including professionally recorded pronunciation for each entry.
Audubon Mammals - A Field Guide to North American Mammals ($9.99, app2.me/2853) In-depth information on 240 species, drawings of mammal tracks, and high-quality photos detailing every species.
Find-A-Fish ($2.99, Lite version available, app2.me/2854) is an easy to use freshwater fish identification guide.
BirdsEye ($19.99, Lite version available, app2.me/2855) Thousands of local birding experts contributions to eBird—the massive, real-time, bird observation system run by the bird experts at the Cornell Lab of Ornithology.
GSM Wildflowers ($4.99, app2.me/2856) covers 178 of the most commonly observed wildflower species within the Great Smoky Mountains of Tennessee and North Carolina.
MyNature Tree Guide ($4.99, app2.me/2857) You can identify over 190 trees with leaves or needles, from Maine to California.
MyNature Animal Tracks ($6.99, app2.me/2377) is a database with 7 searchable track categories—fully illustrated by size and shape for quick selection.
iBird Pro ($29.99; app2.me/256) 4,000 pages of expert birding information at your fingertips. Comprehensive bird ID, behavior, habitat and ecology information.
Dictionary! (Free, app2.me/2915) Includes over 200,000 short and simple definitions, a thesaurus, and an advanced spell check.
Oxford Dictionary of English with audio ($29.99, app2.me/2914) 350,000 words, phrases, and meanings with 70,000 audio pronunciations, 67,000 usage examples, and 11,000 encyclopedia entries.
Merriam-Webster Collegiate Dictionary ($24.99, app2.me/2858) 225,000 definitions, 90,000 entries with audio pronunciations by native speakers.
WordBook English Dictionary & Thesaurus (see "Best of the Best")
Dictionary.com (see "Best of the Best")
Encyclopedia ($4.99, app2.me/3176) Offline access to Wikipedia. It takes up nearly 3 GB, and you have to pay an additional cost to download the updates to the encyclopedia.
iWiki ($1.99, app2.me/2917) Access Wikipedia in 32 languages, save articles for offline viewing, search text within articles, etc.
Wikipedia Mobile (Free, app2.me/2918) is an open source offering from the Wikimedia Foundation that focuses on being simple and fast.
Britannica Concise Encyclopedia 2010 ($19.99, app2.me/2919) Can be read with no Internet connection, has over 25,000 articles, 2,700 images and illustrations, and hyperlinks between articles to help you navigate easily.
Wikipanion ToDo (see "Best of the Best")