Duolingo for Android is a free trending language learning app with which you can easily learn a second or third language. The method of learning is immersive, allowing you to pick up new vocabulary and new expressions with ease. The app tests your memory through a variety of tasks, such as matching definitions, fill-in-the-blank sentences, and conjugations. After each task, you can see your score and, if you succeed, move on to the next step.
Duolingo is also available for iOS devices.