Interlingua is an international auxiliary language (IAL) published in 1951 by the International Auxiliary Language Association (IALA). It is the most widely used naturalistic auxiliary language. Interlingua was developed to combine a very simple grammar with a vocabulary consisting of words that are common to the widest possible range of languages. Interlingua is unusual for being immediately understandable to populations numbering in the hundreds of millions. Conversely, it can be – and is – used as an introduction to similar natural languages.