Koine

The version of the language they spoke, known as Koine Greek, was based on the dialect of Athens.

If a dominant language was spoken in the area of such trade routes, then this dominant language became the ‘interlanguage’, as it is called. Such an interlanguage, or koiné, is a simplified dialect with which speakers of two or more quite different dialects communicate with one another.

Now, another term for that product is koine, which, however, I have regularly […] employed in reference to the infrastructure (procedural, juridical, formal, cultural) that enables and informs composition of a lingua franca. […] In linguistic scholarship koine mostly (!) refers to a standard language expanded by input from several dialectal sources with concomitant levelling of morphological and syntactic differences and adoption of a general and possibly restricted lexicon.