From the Greek, this word means “conversion,” or more clearly, “to change one’s mind, repent, be converted.”
In the modern thinking and teaching of the Church this term has come to mean the relationship of the Christian community within the Church as experienced by individuals.
The first “conversion” is the fundamental gift that one receives in baptism; if this gift is lost through sin, another “conversion” (or return to the ecclesial community) is gained and makes the individual more vigorous in faith through the Sacrament of Penance.
Metanoia is considered fundamental to the pursuit of authentic Christian perfection. It entails true repentance of sin and the subsequent turning toward the Lord. There is a complete change in one’s life, turning from unbelief to belief, a change of heart from sin to the practice of the virtues, and the zealous demonstration of that faith through baptism, confession, and a worthy penance.
Metanoia is commonly used in the Greek New Testament, especially in the preaching of the Apostles. (7:46)