Late in life, the Italian mathematician Giuseppe Peano was the president of an academy devoted to one of these things, which 
Late in life, the Italian mathematician Giuseppe Peano was the president of an academy devoted to one of these things, which Peano also invented. The priest Johann Martin Schleyer claimed to be commanded by God to create one called Volapük. A man who took on the name "Doctor Hopeful," Ludwik Zamenhof, created one of the most successful examples of these things, by eliminating gender and paring down to only one article. For 10 points, Interlingua and Esperanto are some of the most-used examples of what kind of language, along with Elvish and Klingon?
Late in life, the Italian mathematician Giuseppe Peano was the president of an academy devoted to one of these things, which Peano also invented.
{artificial languages} [or {constructed languages}; or {conlangs}; or {international auxiliary languages}]