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 237,000 articles (as of February 5, 2017). Over 150,000 users now 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 over 235,000 registered users, who are able to view the site's interface in their choice of 18 languages. About 47,000 of the lernu.net users possess a basic, intermediate or advanced 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 ten months, the number of learners has more than doubled to 721,000.
Duolingo has also developed an Esperanto course for which the language of instruction is Spanish; public beta testing began in October of 2016. Over 43,300 students are currently beta-testing this course.