Interlinguistics of interlinguistics are, however, not so constructive, but rather descriptive, comparative, historic, sociolinguistic, or concerned with translation by humans or machines. As for Esperanto, which is the most widely used constructed interlanguage, there is a relatively abundant literature about the language itself and its philology (see Esperantology). Only a few of the many constructed languages have been applied practically to any noteworthy extent. The most prosperous were Volapük (1879, Johann Martin Schleyer), Esperanto (1887 Ludwik Lejzer Zamenhof), Latino sine flexione (1903, Giuseppe Peano), Ido (1907, Louis Couturat), Occidental-Interlingue (1922, Edgar de Wahl) and Interlingua (1951, IALA and Alexander Gode), with
L. L. Zamenhof international language must have a simpler grammar. Apart from his parents' native languages Russian and Yiddish and his adopted language Polish, his linguistics attempts were also aided by his mastering of German, a good passive understanding of Latin, Hebrew and French, and a basic knowledge of Greek, English and Italian. By 1878, his project "Lingwe uniwersala" was almost finished. However, Zamenhof was too young then to publish his work. Soon after graduation from school he began to study medicine, first in Moscow, and later in Warsaw. In 1885, Zamenhof graduated from a university and began his practice as a doctor