Concise Bible Dictionary:
The word is διόρθωσις, from “to amend, make right.” Hence the “time of reformation,” or “setting things right.” The thought is taken up from the prophets and will be fulfilled in the kingdom, and implies the setting in order of things on earth according to the mind of God. Christianity is in view and anticipation of this (Heb. 9:10). The Greek verb occurs in the LXX in Isaiah 16:5; Isaiah 62:7; Jeremiah 7:3,5.
Strong’s Dictionary of Greek Words:
Transliteration:
diorthosis
Meaning:
from a compound of 1223 and a derivative of 3717, meaning to straighten thoroughly; rectification, i.e. (specially) the Messianic restauration