There are 3 Greek words used in the New Testament to denote repentance.
Greek: μεταμέλομαι —transliteration: metamelomai
This verb is used of a change of mind, such as to produce regret or even remorse on account of sin, but not necessarily a change of heart. This word is used with reference to the remorse of Judas (Matthew 27:3).
Then when Judas, who had betrayed Him, saw that He had been condemned, he felt remorse and returned the thirty pieces of silver to the chief priests and elders, saying, “I have sinned by betraying innocent blood.” But they said, “What is that to us? See [to that] yourself!” And he threw the pieces of silver into the templesanctuary and departed; and he went away and hanged himself. —Matthew 27:3-5 NASB
Greek: μετανοέω —transliteration: metanoeó or metanoeo
This means to change one’s mind and purpose, a change of the inner man, as the result of after knowledge. This verb, with the cognate noun metanoia —μετάνοια, is used of true repentance, a change of mind and purpose and life, to which remission of sin is promised.
According to Scripture’s teaching of the Gospel, repentance consists of…
Thus he realizes that he is just what God has always seen him to be and declares him to be—a lost sinner who desperately needs God’s mercy. Repentance comprehends not only such a sense of sin, but also an apprehension of mercy, without which there can be no true repentance (Psalms 51:1; 130:4).