A lingua franca is a language that is used widely outside the country where it is spoken as a native language.
French, Greek, Portuguese and Latin have all been major lingua franca at some point in history. The current lingua franca of international business is English.
In the classroom
The position of English as a lingua franca, or international language, and the growth and diversification of other Englishes, has raised many questions about what kind of English learners want and need.