'Frankish tongue'; for plurals see § Usage notes), also known as a bridge language, common language, trade language, auxiliary language, vehicular language, or link language, is a language systematically used to make communication possible between groups of people who do not share a native language or dialect, particularly when it is a third language that is distinct from both of the speakers' native languages.

A lingua franca is a language systematically used to make communication possible between people not sharing a first language, in particular when it is a third language, distinct from both speakers' first languages. Examples of lingua francas are numerous and exist on every continent.

A lingua franca (originally Italian for "Frankish language" - see etymology below) is a language that is used between persons who do not have the same mother tongue. The terms working language, bridge language and vehicular language are used in the same sense.

A lingua franca (from Italian, literally meaning Frankish language, see etymology under Sabir and Italian) is a language systematically used to communicate between persons not sharing a mother tongue, in particular when it is a third language, distinct from both persons' mother tongues.