Translations, clockwise from top left: ① “Anyone can cook” in French; ② “Good night” in Korean; ③ “Why are you eating the yellow snow?” in Czech; ④ “My strange uncle lives in a lighthouse” in Gaelic; ⑤ “All men must die” in High Valyrian

Translations, clockwise from top left: ① “Anyone can cook” in French; ② “Good night” in Korean; ③ “Why are you eating the yellow snow?” in Czech; ④ “My strange uncle lives in a lighthouse” in Gaelic; ⑤ “All men must die” in High Valyrian

Illustration: Seo Inji for Bloomberg Businessweek

Can Duolingo Actually Teach You Spanish?

The free language app has gamified learning French, Gaelic and even High Valyrian. Now the public company must make money without infuriating its fierce following.

After dinner on Aug. 23—a date he will never forget—Tobi Fondse pulled out his phone to do his daily Duolingo. He was studying French on the language-learning app so he’d be able to order croissants au jambon and bière à la pression on his frequent visits to France, “instead of having to point at things,” says the 50-year-old Dutch IT consultant.

He’d tried Babbel, Busuu and other language apps but preferred Duolingo because its lessons were fun. They didn’t feel like a chore. He and his wife, Marisa, had completed at least one lesson for more than 400 consecutive days, placing them among Duolingo’s most dedicated paying users. “I’m deadly serious about learning French,” he says.