A saint is a repentant sinner whose sins have been forgiven (Mark 1:15).
"My dear children, I write this to you so that you will not sin. But if anybody does sin, we have an advocate with the Father—Jesus Christ, the Righteous One."
--1 John 2:1 NIV
A sinner is an unrepentant nonbeliever whose sins are not forgiven (John 3:16-18)
Romans 3:22-24 BSB
22And this righteousness from God comes through faith in Jesus Christ to all who believe. There is no distinction, 23for all have sinned and fall short of the glory of God, 24and are justified freely by His grace through the redemption that is in Christ Jesus.
