Kudos Wiktionary Word of the day APP and WIDGET.

Learn a new word everday by either launching the app or including a widget on your home screen (To add a widget after installing the app tap on an empty part of your background and select 'widgets' then 'Wiktionary')
Tapping the widget will give a full explanation of the word.

Dictionary data taken from wiktionary.com
Parts of the source are taken from or modified versions of that found on the Android Developer Blog.

Get now Python cheat sheets, quick reference cards and learning manuals. All the reference you need to learn Python and consult anything anywhere.

Learn Spanish vocabulary with word cards, pronunciation by native Spanish speakers and exercises to test what you have learned.

+ Clear audio recordings of native Spanish speakers.
+ Very easy to use!
+ Works offline! (data rates while in roaming are expensive. No internet connection needed).
+ You can practice anywhere you go
+ Compressed files to ensure fast download anywhere.

Recommended app for tourists and business people visiting Spain.

A game for both learners of the English language and for native English Speakers. This game of Hangman contains over 17 different topics. Also, includes a button that uses the google translate application to translate the word into the users language.

This is the basic version. it has two in game adds. The full version contains over 18 topics, over 600 words and will be updated regularly with new topics and words.

Online Dictionary - Multiple dictionaries including: English dictionary, medical dictionary, legal dictionary, financial dictionary, computer dictionary, thesaurus, dictionary of acronyms and abbreviations, dictionary of idioms, thesaurus, Columbia encyclopedia, Wikipedia encyclopedia, Hutchinson encyclopedia, examples from classic literature, pronunciations, word browser, glossary. Free access.

Application unofficial The Free Dictionary, thefreedictionary.

English-French offline dictionary

Expand your German vocabulary and gain eloquence and quick-wittedness!

Expand your English vocabulary and gain eloquence and quick-wittedness!

- German-English dictionary contains over 86,000 entries.
- English-German dictionary contains over 93,000 entries.

This application allows you to browse off-line dictionaries. This is useful when the Internet connection is not availabe (abroad, in the plane...)

Learn new words easily and quickly. Take a photo of the dictionary in your language textbook and VocabIT will make flash cards from the photo for you. You can look at your statistic, practice or just browse the vocabulary.

Free Chinese Dictionary, with Word Lists and Flash Cards

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Intelligent English, Chinese and Pinyin search
CC-CEDICT Chinese Dictionary powered
Small footprint, Low battery consumption

Easy Vocabulary can be used as a vocabulary trainer or dictionary in any language.
Import or export word lists in CSV format. Find, add, edit, or delete words.
Learn vocabulary with an index card system in read, select or write mode. Have fun with Easy Vocabulary.

Tiny Classroom Flash Cards is a feature rich flash card application for foreign language study. Tiny Classroom now provides free access to flash card learning lists for 30 separate languages!

+ Flash card mode
+ Written answers
+ Auto play flash cards
+ List View and filters
+ Import flash cards from web
+ Import or edit flash cards on phone

More flash card features coming soon in version 1.3

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Dictionnaire Littré

Ultimate online dictionary with Wiki app for android 1.6+ Fully supports Moto Droid & Nexus 1. Can't find in dictionary? Find it on Wiki Wiki Wiki!

Features:
Droid & Nexus One Support
Text to Speech Keywords
Dictionary & Wiki as backup!
Dictionary Words Update Online
Dictionary find closest match
Now with THESAURUS!

• Anglo-český, česko-anglický "kapesní" slovník bez připojení na Internet.
• English-Czech and Czech-English dictionaries in your pocket without being connected to the Internet.

Multi-languages dictionary, support Stardict, Kdict, Zdict free dictionaries. Word can be added into History and Woodbook. Define custom online-dict to query free web protocol, and online-dict can be exported and imported. Support Recite(random,word fill game...) and Quickbar, you can search anywhere outside of application.

Mobile memory app helps you remember words quickly and efficiently by language learning. It supports Stardict, Kdict, Zdict dictionaries, embeded download system inside Momemo. After learn then go over through test, you can mark word as favorite or set reicte level. Also supports IPA and speech, can be used as dictionary.

The Application is developed to easily learn foreign words. Flash-cards and matching. All dictionaries are downloadable. English-French, English-Spanish, English-Russian, English-Italian. Other language pairs coming soon.