The voluntary self-accusation of one's sins to a qualified priest in order to obtain absolution from him. This accusation must be an external manifestation. It must be objectively complete in that the penitent confesses every mortal sin according to number and kinds that he has committed since his last worthy reception of the sacrament of penance. In extraordinary circumstances a subjectively complete confession is sufficient, that is, when circumstances prevent a person from accusing himself of all his grave sins. He is nevertheless obliged to confess all his mortal sins in a later reception of the sacrament.
When there are no mortal sins to confess, it is sufficient to confess any previous sins from one's past life or any present venial sins of which a person has been guilty, in order to obtain absolution and the grace of the sacrament of penance. (Etym. Latin con-, thoroughly + fateri, to acknowledge: confessio, confession.)