What do you mean by original sin?

The Catholic Answers

Actual sin is a deliberate personal transgression of God’s law. But original sin, which is inherited, does not mean that I have personally and maliciously transgressed. We must notice the difference between nature and grace. Nature is our being and all that our condition demands as rational animals. Grace means a gift or quality over and above all that our nature legitimately demands. Now nature is fitted to know God only by deduction from created things. Yet over and above this God’s sheer goodness chose to give us what is in no way due to us, the supernatural destiny to see Him face to face in heaven, and the grace to attain this Vision. He promised this to Adam and, provided Adam were faithful, to all his children. And in this supernatural matter He regarded Adam as father of the human family. Adam failed. He and his children were deprived of this supernatural destiny and of the gift of sanctifying grace. This deprivation of grace is called original sin. It is called sin in so far as we lack that quality which renders us pleasing in God’s sight as heirs to the Vision of Himself in heaven.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty