Duolingo.

About Duolingo

Duolingo, Inc. is an American educational technology company that produces learning apps and provides language certification. Duolingo offers courses on 42 languages, ranging from English, French, and Spanish to less commonly studied languages such as Hawaiian, Māori, and Navajo, and even constructed languages such as Esperanto and Klingon. It also offers courses on music, math, and chess. The learning method incorporates gamification to motivate users with points, rewards and interactive lessons featuring spaced repetition. The app promotes short, daily lessons for consistent, phased practice.