Duolingo
Duolingo is a language learning app that is free and runs on a freemium model.
DuoLingo: One of the most user-friendly, simplistic and beautiful interface apps with interactive learning. The best part about the app is learning by playing, I have never felt it as a learning app rather I have seen it as a very good game. The streaks help me achieve more and stay motivated. The Product Managers have made the app in a way that is goal-oriented and keeps you motivated to do more while also learning. It even shows politely that this ad helps us keep education free.