Esperanto is the most widely spoken constructed international auxiliary language in the world. Its name derives from Doktoro Esperanto, the pseudonym under which L. L. Zamenhof published the first book detailing Esperanto, the Unua Libro, in 1887. The word esperanto means 'one who hopes' in the language itself. Zamenhof's goal was to create an easy and flexible language that would serve as a universal second language to foster peace and international understanding.
Esperanto has had continuous usage for over a century by a community now estimated at about 2 million speakers, and approximately one thousand native speakers. However, no country has adopted the language officially. Today, Esperanto is employed in world travel, correspondence, cultural exchange, conventions, literature, language instruction, television and radio broadcasting. Also, there is an Esperanto Wikipedia with over 243,000 articles (as of December 1, 2017). About 151,000 users consult the Esperanto Wikipedia regularly.
There is evidence that learning Esperanto may provide a good foundation for learning languages in general. Some state education systems offer basic instruction and elective courses in Esperanto. Esperanto is also the language of instruction in one university, the Akademio Internacia de la Sciencoj in San Marino.
Free on-line courses to teach the international language are available through lernu.net and duolingo.com. The first of these sites has about 259,500 registered users, who are able to view the site's interface in their choice of 19 languages; a further four languages have at least 75 percent of the interface localized; 11 additional languages are in varying stages of completing the interface translation. About 50,000 of the lernu.net users possess at least a basic understanding of Esperanto. On March 25, 2016, when the Duolingo Esperanto course completed its beta-testing phase, that course had 350,000 people registered to learn Esperanto through the medium of English; in the subsequent 21 months, the number of learners more than doubled; the count now stands at 1.13 million.
Duolingo has developed a second Esperanto course for which the language of instruction is Spanish; public beta testing began in October of 2016. More than 258,000 students are currently beta-testing this course. As Chuck Smith, founder of the Esperanto Wikipedia, pointed out, this means that well over a million people are now learning Esperanto through the Duolingo interface. A third Esperanto course, to be taught in Brazilian Portuguese, has begun development and is expected to be released to beta testing by the end of 2017; over 26,000 people have pre-registered to take this course when it becomes available.