This article is intended to help beginners in Ecclesiastical Greek develop a strategy to translate a wide range of Church writings.
The Church fathers used the common written language in use during their time. This was Attic Greek.
There are two caveats though: first there are many sub-dialects in Attic Greek that the translator has to be conscious of. Secondly, many manuscripts were modified by medieval copyists and are mixed-bag of old and newer constructs.
Greek in the ancient world was much like the contemporary English language. There is koine English, which is a base form of English which many countries and regions share very similar commonalities. For example the United States south, British, and Australians can communicate with only a few problems. However, each one does have some distinct words and pronunciations that each party quickly recognizes and makes adjustments. Ecclesiastical Greek has many authors that wrote in their own sub-dialect similar to the slight differences found between British, American and Australian literature.