Google has added offline neural machine translation (NMT) to Translate.
The apps’s neural system will translate whole sentences at a time before using context to help it figure out the most “relevant” translation. The app then rearranges and adjusts the sentence so that it sounds more natural.
Languages packs range from 35-45MB.
Google is rolling out the update in 59 languages over the next few days. Google translate offline featured phrase-based machine translation that will translate blocks or phrases at a time. These phrases were not linguistic or syntax-based which can cause issues during translation.
To try the NMT offline translation, head on over to the Translate app on Android or iOS. For users who have already used offline translations there should be a banner on the home screen that will update the previous files. For users who have not downloaded languages, tap the arrow next to the language name to download the package for that language.
Source: Google Developer Blog