In Koine Greek and Modern Greek, the only remnant of the dual is the numeral for "two", , , which has lost its genitive and dative cases (both , ) and retains its nominative/accusative form. Thus it appears to be undeclined in all cases. Nevertheless, Aristophanes of Byzantium, the foremost authority of his time (early 2nd century BC) on grammar and style, and a staunch defender of "proper" High Attic tradition, admonishes those who write "dysí" (dative, plural number) rather than the "correct" "dyoīn" (dative, dual number).