Esperanto is the most commonly used artificial language. It was created by Polish physician Ludwig L. Zamenhoff and was first presented in 1887. The name of the language comes from the pseudonym (“Doktoro Esperanto”) used by the author in his first textbook. Esperanto can be learned considerably quicker than a typical natural language. The grammar is extremely regular, yet not primitive. There is only one paradigm for nouns and one paradigm for verbs. There is a simple relation between written and spoken text. The word order is “free”, allowing topic-focus articulation.
About 70% of Esperanto vocabulary come from Romance languages, about 20% from Germanic languages and English and some part from Slavic languages. The word-building is very rich and highly regular.
The estimates of the numbers of Esperanto speakers range from 1 to 10 millions. There is about 1000 of native speakers. Several tens of thousands of books have been published in Esperanto (original and translated), and there are many periodicals.
There are several tendencies in the current Esperanto movement:
A conservative group of speakers uses as a measure of the correctness of the language the books written by Zamenhof, including the so-called Fundamento. According to them, current speakers of Esperanto should follow the language in this corpus; even (apparent) Zamenhof's mistakes.
A progressive group is trying to change the language to make it more international, closer to English, easier to use etc. Some of the proposals are unsuccessful, some are partially used and some are even made official by Akademio, the headquarter of the Esperanto world.
There is a third group of Esperanto users: AIL, group of scientists that uses the language for pragmatic reasons and wants to distinguish itself from the first two groups. They call the language ILO (Internacia Lingvo, International language), the original name used by Zamenhof.