PENITENCE, REPENTANCE, CONTRITION, COMPUNCTION, REMORSE mean regret for sin or wrongdoing.

PENITENCE implies sad and humble realization of and regret for one's misdeeds.

e.g. absolution is dependent upon sincere penitence

REPENTANCE adds the implication of a resolve to change.

e.g. repentance accompanied by a complete change of character

CONTRITION stresses the sorrowful regret that constitutes true penitence.

e.g. tearful expressions of contrition

COMPUNCTION implies a painful sting of conscience especially for contemplated wrongdoing.

e.g. had no compunctions about taking back what is mine

REMORSE suggests prolonged and insistent self-reproach and mental anguish for past wrongs and especially for those whose consequences cannot be remedied.

e.g. thieves untroubled by feelings of remorse

deep regret or guilt for a wrong committed:

«…への» 自責の念, 深い後悔, 良心の呵責（かしゃく） «for» (!regretより強い後悔)

e.g. they were filled with remorse and shame.

late Middle English: from Old French remors, from medieval Latin remorsus, from Latin remordere ‘vex’, from re- (expressing intensive force) + mordere ‘to bite’.