Hello,
This app is built carefully and comes with many useful features for learning vocabulary:
Spaced Repetition
Quiz mode
Two mini-games to brush up vocabulary
Auto syncing/backup
Offline access
Built-in dictionary
Built-in translation
and so on
It's free, clean and available on both iOS and Android. For the list of supported languages, please see the description on the app page of App Store or Play Store.
There are more screenshots on the landing page that you can checkout first.
App preview:
Landing page: https://ulangi.com
iOS: https://itunes.apple.com/us/app/id1435524341?mt=8
Android: https://play.google.com/store/apps/details?id=com.ulangi
Thank you.