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Introduction

The Google Translate app for iOS and Android devices offers powerful and impressive machine translation capabilities. It is a free download

Download:

Google Translate for Android and iOS offer similar features:

You can point your device's camera to a image with text (from a street sign or menu for example), and the Translate app will automatically translate the text and overlay the translated text on the screen. This is the technology from Word Lens which Google acquired some time ago. Instant translation currently works for translation from English to and from French, German, Italian, Portuguese, Russian, Spanish, Bulgarian, Catalan, Croatian, Czech, Danish, Dutch, Filipino, Finnish, Hungarian, Indonesian, Lithuanian, Norwegian, Polish, Romanian, Slovak, Swedish, Turkish and Ukrainian. This works without Internet access.
For other languages not supported Google Translate app can still scan a photo taken from your phone and to get a translation of it in 37 languages.

words or phrases can be translated by typing them into app. This requires Internet access, however a phrasebook of past translations can be stored for viewing when you're offline.

Google Translate can interpret spoken words or phrases and can speak the translated text. This can allow for two persons to have a bilingual conversation where Google Translate can listen to either language and speak an interpreted version in the other language. This requires Internet access.

if you don't know how to type characters, you can draw characters on your device's screen and see their translation. This requires Internet access

See Google Translate Help for more details on how to use those features.

Google Translate for Android offers additional features:

The Android version of Google Translate allows for downloading of languages for offline translation when words or phrases are typed in. See https://support.google.com/translate/answer/6142473?hl=en
Google Translate can translate text within other apps such as TripAdvisor, WhatsApp and LinkedIn. See related blog post