Proper noun
Attic Greek
The dialect of Ancient Greek used in Attica, the region surrounding Athens, from 500 to 300 BC, closely related to Ionic Greek and a main contributor to Koine Greek. The language of Thucydides, Plato, Aeschylus, Xenophon, etc.
Liddell, Henry George ; Scott, Robert ; A Greek–English Lexicon at the Perseus Project Mastronarde, Donald J. Introduction to Attic Greek. Source: Internet
They avoided vocabulary unknown to Attic Greek and inserted an explanation when they had to use contemporary words. Source: Internet