Web page and text translator, dictionary, grammar checker, auto translation, text-to-speech, and language learning services. Supports over 3,000 unique language pairs and 31 online translators, including Google Translate, Wikipedia, and Babylon.
Languages: Arabic, Chinese, Czech, Danish, Dutch, English, French, German, Greek, Hebrew, Hungarian, Icelandic, Italian, Japanese, Korean, Norwegian, Polish, Portuguese, Romanian, Russian, Spanish, Swedish, Turkish, Ukrainian
I don't recommend Firefox add-ons very often but this one is a winner taking care of all your language needs. Spelling, definitions, translate