Meaning

verb math: determine the length of

verb reduce to a fine, unmixed, or pure state; separate from extraneous matter or cleanse from impurities

verb bring, lead, or force to abandon a wrong or evil course of life, conduct, and adopt a right one

originFrom Middle English rectifien, from Anglo-Norman rectifiier, rectefier (“to make straight”), from Medieval Latin rēctificō (“to make right”), from Latin rēctus (“straight”).

Etymology from Wiktionary, CC BY-SA 3.0