- A common language used by people of diverse backgrounds to communicate with one another, often a basic form of speech with simplified grammar, particularly, one not the first language of any of its speakers.
- The most common plural form in English is lingua francas; however, the plural forms lingue franche (following the Italian) and linguae francae (in the style of Latin) are both fairly common as well. Also attested, but quite rare, and probably nonstandard, is the form linguas franca (treating lingua alone as the noun and taking franca as an adjective; compare attorneys general, forests primeval).
- (common language): vernacular
- the Mediterranean Lingua Franca, a common language spoken in Mediterranean ports in centuries past (consisting of Italian mixed with French, Spanish, Arabic and some Greek words and used by sailors of different countries to communicate with one another)
- (historical) Mediterranean Lingua Franca (common language spoken in Mediterranean ports in centuries past)
- lingua franca (common language)