Repentance is the activity of reviewing one's actions and feeling contrition or regret for past wrongs. Today, it is generally seen as involving a commitment to personal change and the resolve to live a more responsible and humane life. In other words, being sorry for one's misdeeds. But it can also involve sorrow over a specific sin or series of sins that an individual feels he or she has committed. The practice of repentance plays an important role in the soteriological doctrines of Judaism, Christianity, and Islam, where it is often considered necessary for the attainment of salvation. Analogous practices have been found in other world religions as well. In religious contexts it often involves an act of confession to God or to a spiritual elder (such as a monk or priest). This typically includes an admission of guilt, a promise or resolve not to repeat the offense; an attempt to make restitution for the wrong, or in some way to reverse the harmful effects of the wrong where possible. As such, it can be seen as having a certain relationship to modern day therapeutic practices though it clearly differs in its particulars.
In Biblical Hebrew, the idea of repentance is represented by two verbs: שוב shuv (to return) and נחם nacham (to feel sorrow). In the New Testament, the word translated as 'repentance' is the Greek word μετάνοια (metanoia), "after/behind one's mind", which is a compound word of the preposition 'meta' (after, with), and the verb 'noeo' (to perceive, to think, the result of perceiving or observing). In this compound word, the preposition combines the two meanings of time and change, which may be denoted by 'after' and 'different'; so that the whole compound means: 'to think differently after'. Metanoia is therefore primarily an after-thought, different from the former thought; a change of mind and change of conduct, "change of mind and heart", or, "change of consciousness".
The doctrine of repentance as taught in the Bible is a call to persons to make a radical turn from one way of life to another. The repentance (metanoia) called for throughout the Bible is a summons to a personal, absolute and ultimate unconditional surrender to God as Sovereign. Though it includes sorrow and regret, it is more than that. It is a call to conversion from self-love, self-trust, and self-assertion to obedient trust and self-commitment to God. It is a change of mind that involves a conscious turning away from wrong actions, attitudes and thoughts that conflict with a Godly lifestyle and biblical commands, and an intentional turning toward doing that which the Bible says pleases God. In repenting, one makes a complete change of direction (180° turn) toward God. The words "repent," "repentance," and "repented" are mentioned over 100 times in the Bible.