Esperanto () is the world's most widely spoken constructed international auxiliary language. Created by L. L. Zamenhof in 1887 to be 'the International Language' (la Lingvo Internacia), it is intended to be a universal second language for international communication. He described the language in Dr. Esperanto's International Language (Unua Libro), which he published under the pseudonym Doktoro Esperanto. Early adopters of the language liked the name Esperanto and soon used it to describe his language. The word translates into English as 'one who hopes'.
Within the range of constructed languages, Esperanto occupies a middle ground between "naturalistic" (imitating existing natural languages) and a priori (where features are not based on existing languages). Esperanto's vocabulary, syntax and semantics derive predominantly from languages of the Indo-European group. A substantial majority of its vocabulary (approximately 80%) derives from Romance languages, but it also contains elements derived from Germanic, Greek, and Slavic languages. One of the language's most notable features is its extensive system of derivation, where prefixes and suffixes may be freely combined with roots to generate words, making it possible to communicate effectively with a smaller set of words.