Duolingo

What if you could convert some of the time you spend on your phone, aimlessly scrolling through social media or playing games, into something enriching, like learning a new language? That’s the bet entrepreneur Carnegie Mellon computer science professor Luis von Ahn made with Duolingo—and he was right: the digital language-learning program now has 300 million users, up from about 200 million a year ago. Duolingo offers English speakers lessons in 27 different tongues, from Danish to Spanish to Welsh. And it’s free, supported by ads on the platform (users can pay $9.99 a month for an ad-free experience). Duolingo “gamefies” the instruction; users earn points and virtual currency as they learn. “We’re using a lot of the techniques that games like Angry Birds use to get you addicted,” says von Ahn, “but to learning a language.” It’s fun—but for many people, it’s also a lifeline. Duolingo has become popular among Syrian refugees settling in new countries: the company has created courses in English, French, German and Swedish for Arabic speakers. —Sean Gregory