Latin: indulgere, to be kind

The remission of temporal punishment due to sin after its guilt has been forgiven, which the Church grants from the treasury of the merits of Christ and His saints. A plenary indulgence is the remission of the whole debt of temporal punishment. A partial indulgence remits only a part of that punishment. An indulgence of 40 days, for example, remits so much of temporal punishment as would be remitted by performing the ancient canonical penances for 40 days. In granting an indulgence to the living, the Church offers satisfaction to God from her treasury of merit, so that such an indulgence is a real juridical absolution from temporal punishment. Indulgences for the dead are gained by way of intercession (per modum suffragii), i.e., the Church offers satisfaction from her treasury of merit and asks God to apply this satisfaction to the souls in purgatory. An indulgence for the living, if all conditions are fulfilled, produces its effect infallibly, while that for the dead, because departed souls are not under the Church’s jurisdiction, depends on the good pleasure of God. Besides the habitual intention, the state of grace and the performance of the prescribed good works, prayers, alms, visits to a church, etc., are required to gain an indulgence. Confession and Communion are required for a plenary indulgence. Confession twice a month and Communion five or six times a week suffice for all plenary indulgences except for the jubilee indulgence. See also

Key of Heaven: What An Indulgence Is

By an Indulgence is meant the remission of the temporal punishment due to us on account of our sins. Every sin, however grievous, is remitted through the sacrament of penance, or by an act of perfect contrition, as regards its guilt and the ternal punishment due to it. But the debt of temporal punishment is not always remitted at the same time. This latter is done away with by deep penitence, or by works of satisfaction, e.g. prayers, alms, fasting, etc.; or by the patient endurance of troubles and adversities sent us by God, etc.; or by the satisfaction of our Lord Jesus Christ and the saints, applied to us through Indulgences by those who have the power to apply them. And although, in order to escape this temporal punishment, we must not rely on Indulgences alone, to the neglect of good works; yet, because, at the best, our own good works are very imperfect, and the debt of punishment due to us very great, we ought to endeavour, as frequently as possible, to avail ourselves of the benefits of Indulgences. Indulgences are of two kinds: 1st, a plenary Indulgence, when guly gained, is a full and entire remission of all the temporal punishment due to sin. The eight Indulgences granted to the faithful at the principal festivals in the year, are plenary Indulgences. A jubilee is also a plenary Indulgence occasionally granted by the POpe to the whole Church, in the most ample manner and with the greatest solemnity. There are many other plenary INdulgences granted to various good works. 2nd, a partial or limited Indulgence, as of ten years of a hundred days, etc., remits as much of the temporal punishment as would have been remitted by ten years, or a hundred days, etc., of the canonical penances formerly imposed on public penitents.

What Is Required to Obtain an Indulgence

1. A Plenary Indulgence: to approach to the sacraments of penance and the Holy Eucharist; to perform the special work to which the Indulgence is attached. Most plenary indulgences have attached to them as a condition that we are to pray for the intention of the Holy Father. For this purpose, we may say a litany, a portion of the rosary, Jesus psalter, or five Paters and five Aves. One Communion suffices fo rseveral Indulgences, if they can be gained on the same day.

2. Partial Indulgence: to be in a state of grave; to perform the work to which the Indulgence is attached.

N.B.: Power is general given to confessors to change the works for some others, in the case of the sick, or persons who are confined, and who cannot therefore fulfill some of the cnditions, such as fasting or visiting certain churches.

The Disposal of our Indulgences

We may apply our Indulgences to ourselves, or we may in many cases apply them to the relief of the holy souls in purgatory. Those who embrace “The Heroic Act of Charity”, by which they renounce for themselves and apply to the relief of the holy souls the merits of all their good works, have the privilege of likewise being able to apply to them all the Indulgences they gain. Even if our devotion does not lead us to follow this, we must be most careful never to forget the holy suffering souls.

– from Key of Heaven: A Manual of Devout Prayers, Saint Joseph’s Shrine of Mount Royal, Montreal, Canada, 1915