The Greek diorthosis (G1357) means a setting straight, a reformation, or a correction — bringing something back to its proper order. In Hebrews 9:10, it describes the eschatological 'new order' inaugurated by Christ's high priestly work.
Diorthosis in Hebrews 9:10 is a crucial argument: the Levitical regulations were external ordinances applying 'until the time of the new order (diorthosis).' The old covenant's sacrifices were always provisional, pointing to the true cleansing that only Christ's blood could accomplish. The Messiah's coming is described as the great diorthosis — the divine reformation that sets all things right.