Yarn is for lazy (& busy) language learners.It lets you learn foreign language while you browse in English. It lets user continue reading what they already read while enabling them to improve their vocabulary in a foreign language...
See More . It has scoured millions of webpages and video subtitles to build a difficulty-graded list of the 100,000 most important words in the English language. As you browse the web with Yarn, it prompts you to test your knowledge of translations (in your target language) of words from the page you’re reading. And because Yarn learns your ability level, it tests you on exactly the words you need to learn.