What is the term for a language that is a second language for most people?

What is the term for a language that is a second language for most of the people that use it? For example, when the Portuguese traded with East African countries in the 1700's, none of them spoke their mother tongue. English can also been seen as this type of language. It is two words and sounds Latin.


lingua franca

From the Merriam Webster dictionary:

lin·gua fran·ca \ˈliŋ-gwə-ˈfraŋ-kə\

noun

: a language that is used among people who speak various different languages

Full Definition

  1. often capitalized : a common language consisting of Italian mixed with French, Spanish, Greek, and Arabic that was formerly spoken in Mediterranean ports

  2. : any of various languages used as common or commercial tongues among peoples of diverse speech

  3. : something resembling a common language

Plural: lingua francas or lin·guae fran·cae -gwē-ˈfraŋ-(ˌ)kē\

Examples

English is used as a lingua franca among many airline pilots.

Origin: Italian, literally, Frankish language.

First use: 1619