Interlingua is an international auxiliary language

International auxiliary language

An international auxiliary language or interlanguage is a language meant for communication between people from different nations who do not share a common native language...

 (IAL), developed between 1937 and 1951 by the International Auxiliary Language Association

International Auxiliary Language Association

The International Auxiliary Language Association was founded in 1924 to "promote widespread study, discussion and publicity of all questions involved in the establishment of an auxiliary language, together with research and experiment that may hasten such establishment in an intelligent manner and...

 (IALA). It ranks among the top three most widely used IALs (after Esperanto

Esperanto

is the most widely spoken constructed international auxiliary language. Its name derives from Doktoro Esperanto , the pseudonym under which L. L. Zamenhof published the first book detailing Esperanto, the Unua Libro, in 1887...

 and perhaps Ido

Ido

Ido is a constructed language created with the goal of becoming a universal second language for speakers of different linguistic backgrounds as a language easier to learn than ethnic languages...

), and is 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, making it unusually easy to learn, at least for those whose native languages were sources of Interlingua's vocabulary

Vocabulary

A person's vocabulary is the set of words within a language that are familiar to that person. A vocabulary usually develops with age, and serves as a useful and fundamental tool for communication and acquiring knowledge...

 and grammar.