Archaic KJV Word
Repent
Modern equivalent: feel sorry
What Was Lost
The physical turning. Shuv was a direction word -- you were walking away from God, and repentance meant you physically turned around and walked back. Metanoia meant your entire mind was renovated. Neither word was primarily about feeling bad. Both were about radical, total reorientation of life toward God.
Closest Survivor in Modern English
repent (still used but associated with guilt rather than transformation)
Peak Usage (1611)
KJV Matthew 4:17 -- 'Repent: for the kingdom of heaven is at hand'; Acts 2:38 -- 'Repent, and be baptized'
Died still used but distorted (~1800)
Hebrew shuv ('turn around/return') and Greek metanoia ('change of mind/fundamental reorientation') were reduced to 'feel sorry for what you did.' Repentance became an emotion rather than a direction change.
What Replaced It
“feel sorry”
Emotional response only; shuv was a physical turning -- reversing the direction of your entire life
“regret”
Backward-looking; repentance was forward-looking -- turning toward God, not just mourning the past
“apologize”
Social nicety; metanoia was a total transformation of how you think and see reality