LINGUA FRANCA. [The plural is usually lingua francas, but sometimes Italian lingue franche and Latin linguae francae.]
1. Originally, a name for the mixed language, based on ITALIAN and Occitan (Southern French), used for trading and military purposes in the Mediterranean in the Middle Ages. See SABIR.

2. By extension, a semi-technical term for any additional (often compromise) language adopted by speakers of different languages, as a common medium of communication for any purposes and at any level. A lingua franca may be either a fullyfledged language (LATIN in the Roman Empire, Hausa at the present time in West Africa), or a PIDGIN or CREOLE (TOK PISIN in Papua New Guinea, KRIO in Sierra Leone). A language may become somewhat reduced if it is widespread as a lingua franca (SWAHILI in East Africa). FRENCH served widely in Europe as the lingua franca of diplomacy in the 18–19c, and English now serves as a lingua franca in many countries with linguistically diverse populations (such as India and Nigeria) and for many purposes (as with the restricted variety SEASPEAK, used by the world's merchant marine). See BUSINESS ENGLISH, LINGO, LINK LANGUAGE, POLARI.

lin·gua fran·ca / ˈlinggwə ˈfrangkə/ • n. (pl. lin·gua fran·cas) a language that is adopted as a common language between speakers whose native languages are different. ∎  hist. a mixture of Italian with French, Greek, Arabic, and Spanish, formerly used in the Levant.

lingua franca Language that serves as a medium of communication between people who otherwise lack a common tongue. A lingua franca may be a simplified form of the language of the dominant power, such as Pidgin English, or it may be a hybrid, such as Swahili, which consists of words of both Arabic and Bantu origins.

Lingua Franca a mixture of Italian with French, Greek, Arabic, and Spanish, formerly used in the Levant; lingua franca now denotes a language that is adopted as a common language between speakers whose native languages are different.

Recorded from the late 17th century, the phrase comes from Italian, and means literally ‘Frankish tongue’.

lingua franca orig. mixed jargon based on Italian, used in the Levant. XVII. — It., ‘Frankish tongue’; see FRANK.