1) Koine 2) Language 3) Lingua franca 4) Linguistic communication 
Interlanguage - is the term for a dynamic linguistic system that has been developed by a learner of a second language (or L2) who has not become fully proficient yet but is approximating the target language: preserving some features of their first language (or L1), or overgeneralizing target language rules in speaking or writing the target languag...
the learner’s linguistic system as a GRAMMAR in its own right rather than as a defective version of the target language.
The language a learner uses before mastering the foreign language; it may contain features of the first language and the target language as well as non-standard features.
a language created or used for international communication. · (in second-language acquisition) the linguistic system characterizing the output of a nonnative speaker at any stage prior to full acquisition of the target language.