Immortality – Freedom from death or the capacity to decay and disintegrate. Absolute immortality is possessed by God alone, who has no body and whose spirit is eternal by essence. He cannot not exist; he always has been and must be. Natural immortality belongs to all spiritual beings, namely the angels and human souls, who are created indeed and therefore begin, but since they are simple by nature and have no parts, they will not die, although absolutely speaking, they could be annihilated by an act of God.
Gratuitous immortality is a special grace, given originally by God to the ancestors of the human race and restored by Christ as a promise after the last day. It means freedom from bodily death and from separation of the soul from the human body.