Definition - The dialect of Attic Greek (specifically, the dialect of Athens) that became the lingua franca for the eastern Mediterranean after Alexander's conquests and throughout the Roman period.
Note: It was the language that the New Testament was written in.

Etymology -
The term derives from the Greek phrase koine dialektos, common language. Note that koine is the feminine singular of koinos, common or ordinary.

Oxford English Dictionary -
Its first citation is from 1886:
"As might be expected, this koine, like the koine of the Greeks, has a comparatively limited vocabulary.
(Encycl. Brit. XXI. 653/1)

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