Atticism (meaning "favouring Attica", the region of Athens in Greece) was a rhetorical movement that began in the first quarter of the 1st century BC.
It may also refer to the wordings and phrasings typical of this movement, in contrast with various contemporary forms of Koine Greek (both literary and vulgar), which continued to evolve in directions guided by the common usages of Hellenistic Greek.
Although the plainer language of Atticism eventually became as belabored and ornate as the perorations it sought to replace, its original simplicity meant that it remained universally comprehensible throughout the Greek world.
Admired and popularly imitated writers such as Lucian also adopted Atticism, so that the style survived until the Renaissance, when it was taken up by non-Greek students of Byzantine immigrants.
Represented at its height by rhetoricians such as Dionysius of Halicarnassus, and grammarians such as Herodian and Phrynichus Arabius at Alexandria, this tendency prevailed from the 1st century BC onward, and with the force of an ecclesiastical dogma controlled all subsequent Greek culture, even so that the living form of the Greek language, even then being transformed into modern Greek much later, was quite obscured and only occasionally found expression, chiefly in private documents, though also in popular literature.