Just about two years ago we introduced neural machine translation (NMT) to Google Translate, significantly improving accuracy of our online translations. Today, we’re bringing NMT technology offline—on device. This means that the technology will run in the Google Translate apps directly on your Android or iOS device, so that you can get high-quality translations even when you don’t have access to an internet connection.

https://www.blog.google/products/translate/offline-translations-are-now-lot-better-thanks-device-ai/