Latino sine flexione ("Latin without inflections"), Interlingua de Academia pro Interlingua (IL de ApI) or Peano's Interlingua (abbreviated as IL) is an international auxiliary language compiled by the Academia pro Interlingua under the chairmanship of the Italian mathematician Giuseppe Peano (1858–1932) from 1887 until 1914. It is a simplified version of Latin, and retains its vocabulary.
Interlingua-IL was described in the journal Revue de Mathématiques in an article of 1903 entitled De Latino Sine Flexione, Lingua Auxiliare Internationale (meaning On Latin Without Inflection, International Auxiliary Language), which explained the reason for its creation. The article argued that other auxiliary languages were unnecessary, since Latin was already established as the world's international language. The article was written in classical Latin, but it gradually dropped its inflections until there were none.