Interlingua (ISO 639 language codes ia, ina) is an international auxiliary language (IAL) developed between 1937 and 1951 by the International Auxiliary Language Association (IALA). It is the second or third most widely used IAL, after Esperanto and perhaps Ido, and the most widely used naturalistic IAL: in other words, its vocabulary, grammar, and other characteristics are largely derived from natural languages. Interlingua was developed to combine a simple, mostly regular grammar with a vocabulary common to the widest possible range of languages.
The name Interlingua comes from the Latin words inter, meaning between, and lingua, meaning tongue or language. These morphemes are identical in Interlingua. Thus, Interlingua would be "between language", or intermediary language.
With Interlingua an objective procedure is used to extract and standardise the most widespread word or words for a concept found in a set of control languages: English, French, Italian, Spanish and Portuguese, with German and Russian as secondary references. Words from any language are eligible for inclusion, so long as their internationality is shown by their presence in these control languages. Hence, Interlingua includes such diverse word forms as the Japanese geisha and samurai; the Arabic califa; the Aboriginal kanguru; and the Finnish sauna.
Interlingua combines this pre-existing vocabulary with a minimal grammar based on the control languages. People with a good knowledge of a Romance language, or a smattering of a Romance language plus a good knowledge of the international scientific vocabulary, can frequently understand it immediately on reading or on hearing it. Educated speakers of English also enjoy this easy comprehension.
The American heiress Alice Vanderbilt Morris (1874–1950) became interested in linguistics and the international auxiliary language movement in the early 1920s, and in 1924, Morris and her husband, Dave Hennen Morris, established the non-profit International Auxiliary Language Association (IALA) in New York City. Their aim was to place the study of IALs on a scientific basis. Morris developed the research program of IALA in consultation with Edward Sapir, William Edward Collinson, and Otto Jespersen.
The vocabulary and verb conjugations of Interlingua were first presented in 1951, when IALA published the finalised Interlingua Grammar, and the 27,000-word Interlingua-English Dictionary (IED). In 1954, IALA published an introductory manual entitled Interlingua a Prime Vista ("Interlingua at First Sight").
- Union Mundial pro Interlingua, the official site of the Union Mundial pro Interlingua (UMI)
- Academia pro Interlingua