Koine is simply the Greek word for “common.” Many people may recognize the word koine from the word koinonia, which means “fellowship.” Fellowship is having something in common.
Koine Greek was simply the common language of the Mediterranean world in the first century. As Alexander the Great conquered the “civilized world” of his time, he spread Greek language and culture. Much like English has become today, Greek became the most common and pervasive “international language” of the day. Since most people could understand Koine, it was uniquely suited to proclaim the gospel throughout the world.