(IALs)) Esperanto eo, epo 1887 L. L. Zamenhof Fluent speakers: between 30,000 and 300,000 [ 1 ] ; Casual users: est. 100,000 to 2 million; native : 200 to 2000 (1996, est.) [ 2 ] . The most popular constructed language. Idiom Neutral   1902 Waldemar Rosenberger A naturalistic IAL by