38 Peter said to them, “Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit. Acts 2:38 (NASB)
The word repent in v38 (above) translates μετανοήσατε (metanoēsate) the second plural, aorist active imperative case of μετανοέω (metanoeō) which means, “to change one’s mind.” This word is rarely found in Classical Greek because Greek society never thought of a radical change in a man’s life as a whole, of conversion or turning around….
In fact, the whole concept of conversion is not found in Greek thought, but is derived from the New Testament. The idea μετανοέω, then, is to turn around, change one’s mind, relent, and in the theological sense involves “regret or sorrow, accompanied by a true change of heart toward God.