(Latin: gratia, favor)
In its widest meaning, the term signifies any gratuitous gift of God to a rational creature, the bestowal of which is motivated by divine benevolence, whether the gift be natural or supernatural, internal or external to the recipient.
In its strict and ordinary sense, however, grace is a supernatural gift of God's beneficence, gratuitously bestowed upon a rational creature (angel or man), for the ultimate purpose of fitting the recipient for life eternal.
It may be inward or external, as is explained under these titles: Inward grace is either actual or habitual, according as it consists in a transitory help conferred for the performance of a good act, or in an abiding perfection elevating the recipient in a manner to a divine plane of being.
This latter is usually called sanctifying grace, because of its formal effect on the recipient.
Its very presence sanctifies him, makes him holy, a child of God, and an heir of heaven.
Sanctifying grace is always accompanied by the infused virtues and the gifts of the Holy Ghost, both of which share in the general nature of supernatural grace.
They are permanent perfections of the recipient's spiritual faculties" intellect and will, bearing a somewhat similar relation to sanctifying grace as the natural faculties and their dispositions bear to the soul.
Hence by sanctifying grace, and its concomitant gifts, the recipient is in a manner constituted a supernatural nature, a complete radical principle of salutary action.
In reference to its origin, a distinction is made between the grace of God and the grace of Christ.
All grace comes indeed from God, but since the fall every grace bestowed upon human beings is based on the merits of Christ.
Before the fall Adam received grace directly from God, without reference to the Saviour of mankind; and so did the angels whilst they were oh probation.
But now we, the children of the fallen Adam, receive grace only through Christ Our Lord.
Grace is so necessary that without it we cannot do anything for life eternal.
Hence the words of Christ: "Without me you can do nothing" (John 15).
New Catholic Dictionary