common language; lingua franca
Refers to a language used for communication between groups with different native languages, such as English in international settings or a regional trade language.
English is used as an international common language.
Swahili is one of the lingua francas of East Africa.
standard language; national standard variety
In Japanese linguistics, often contrasted with 方言 (dialect); refers to the standardized form of a language understood nationwide, such as 標準語.
In Japan, the common language based on the Tokyo dialect is understood nationwide.
At school, students are instructed to speak the standard language.
In this region, English has become the common language.
TV announcers are expected to speak in the standard language.
At international conferences, English is often used as the common language.