A lingua franca (or working language, bridge language, vehicular language) is a language systematically used to make communication possible between people not sharing a mother tongue, in particular when it is a third language, distinct from both mother tongues.

"Lingua franca" is a functionally defined term, independent of the linguistic history or structure of the language: though pidgins and creoles often function as lingua francas, many such languages are neither pidgins nor creoles. Whereas a vernacular language is used as a native language in a single speaker community, a lingua franca goes beyond the boundaries of its original community, and is used as a second language for communication between communities. For example, English is a vernacular in the United Kingdom, but is used as a vehicular language (that is, a lingua franca) in the Philippines.

International auxiliary languages such as Esperanto have historically had such a low level of adoption and use that they can only be described as potential rather than functioning lingua francas.

Franca is a large city in the Brazilian state of São Paulo, located at 20º32'19"S; 47º24'03'W at 1040 m altitude, founded in 1805 . Estimated population in 2008 was 327,176 inhabitants. Franca is the municipal seat of Franca municipality.

The history of the region of Franca begins at the time of the Bandeirantes explorers. The bandeira or entrada of Anhangüera (the son) in 1722 established the “way of Goiás,” a trail from São Paulo to the gold mines in Goiás. Along this and other trails settlements were made, becoming the so-called "landings" or way-stations for the gold seekers. Franca was known at the time of the Bandeirantes as the “catfish landing.”

At the end of the 18th century, settlers had dispersed into the region in several of these landings. In 1779, around 1000 people lived in the area around Franca . To better organize the settlement, a Decree Company was created and the Portuguese Captain Manoel de Almeida was put in charge. At the beginning of the 19th century, the sons of Manoel de Almeida (Antonio Antunes de Almeida and Vicente Ferreira de Almeida) donated lands for the construction of a chapel, which in turn was blessed by the priest Joaquin Martins Rodrigues. With the decline of mining activity in Minas Gerais and Goiás, more settlers migrated to the "Belo Sertão do Rio Pardo" (beautiful valley of the Pardo River), under the sponsorship of the governador of São Paulo, Antônio José de Franca e Horta, after whom the city and municipality are named.