This article is from the sci.lang FAQ, by Michael Covington (email@example.com) and Mark Rosenfelder (firstname.lastname@example.org) with numerous contributions by others.
Hundreds of constructed languages have been devised in the last few centuries.
Early proposals, such as those of Lodwick (1647), Wilkins, or Leibniz, were
attempts to devise an ideal language based on philosophical classification
of concepts, and used wholly invented words. Most were too complex to learn,
but one, Jean Francois Sudre's Solresol, achieved some popularity in the last
century; its entire vocabulary was built from the names of the notes of
the musical scale, and could be sung as well as spoken.
Later the focus shifted to languages based on existing languages, with a
polyglot (usually European) vocabulary and a simplified grammar, whose purpose
was to facilitate international communication. Johann Schleyer's Volapu"k
(1880) was the first to achieve success; its name is based on English
("world-speech"), and reflects Schleyer's notions of phonetic simplicity.
It was soon eclipsed by Ludwig Zamenhof's Esperanto (1887), whose grammar
was simpler and its vocabulary more recognizable. Esperanto has remained
the most successful and best-known artificial language, with a million or
more speakers and a voluminous literature; children of Esperantists have
even learned it as a native language.
Its relative success hasn't prevented the appearance of new proposals, such
as Ido, Interlingua, Occidental, and Novial. There have also been attempts
to simplify Latin (Latino Sine Flexione, 1903) and English (Basic English,
1930) for international use. The recent Loglan and Lojban, based on
predicate logic, may represent a revival of a priori language construction.
See also Andrew Large, THE ARTIFICIAL LANGUAGE MOVEMENT (1985); Mario Pei,
ONE LANGUAGE FOR THE WORLD (1958); Detlev Blanke, INTERNATIONALE
PLANSPRACHEN (in German). For websites, see the web version of the FAQ.
There is a newsgroup, soc.culture.esperanto, dedicated to Esperanto. Also
see alt.language.artificial, dedicated to artificial languages in general.
The ConLang mailing list is devoted to the discussion of constructed and
artificial languages for general communication; its FAQ is on the web at
http://personalweb.sierra.net/~spynx/FAQ/index.html. To subscribe,
e-mail a message to email@example.com consisting of the single
line: subscribe conlang
The AuxLang list is devoted to discussions of the merits and
practicality of particular international auxiliary languages. To
subscribe, send mail to firstname.lastname@example.org consisting of the
single line: subscribe auxlang