interlanguage

noun

1. A language generated by a student of a foreign language that incorporates aspects of their native language and the target language.

   “Trasyanka and Surzhyk are interlanguages: a Belarusian–Russian and a Ukrainian–Russian mixed language.”

   “The learner's selection from his/her store of interlanguage rules is not haphazard but systematic and predictable, based as it is on his/her existing rule system in much the same way as the native speaker bases his/her speech on the internalized knowledge of the L1 system.”

2. A lingua franca, a common language used by speakers of different languages

   “Latin used to be the European interlanguage. Currently English widely serves this purpose.”

   “As [David] Bellos points out, those born as English speakers are now a minority of English speakers: most speak it as a second language. English is the world’s biggest interlanguage.”

3. A pidgin or creole