The Greek adjective ametamelētos is a compound of a- (not) and metamelomai (to regret, repent, change one's mind), meaning that which is not regretted, cannot be revoked, or is not subject to change of mind. It occurs twice in the New Testament — once applied to God's gifts and calling, and once to human repentance.
Romans 11:29 — 'for God's gifts and his call are irrevocable' — is one of the most comforting statements in Scripture concerning divine faithfulness. The context is Paul's argument about Israel's future: despite their current rejection of the Gospel, God has not revoked His covenant promises. The theological principle applies universally: what God has given and called, He does not take back. This grounds the doctrine of perseverance — God's commitment to complete what He has begun (Philippians 1:6). In 2 Corinthians 7:10, the related word ametamelēton describes the godly sorrow that 'leads to salvation and leaves no regret' — true repentance that one need not regret having done.