The two are different in vocabulary and grammar. Koine Greek is much easier than classical Greek. It is the baseline for modern language, pronunciation, and grammar. Koine Greek was initially established within the armies of Alexander the Great.
Koine Greek is thought of as the first supra-regional dialect in Greece and served as a conversational speech for the Eastern Mediterranean religion and the near East. This language is also said to be biblical. The grammar of modern Greek has its roots in Koine Greek. Koine Greek was more academic than its modern predecessor. The standardized form of Greek is also termed Standardized Modern Greek. It was the end of the medieval period that ushered in the language of Modern Greek. It is often correlated with the fall of the Byzantine Empire. .Koine Greek is believed to be the language of life, while modern Greek can be called the books' language.