Actual sin is sub-divided into greater sins, called mortal, and lesser sins, called venial.
When we neglect things commanded our sin is called a sin of omission. Such sins as willfully neglecting to hear Mass on Sundays, or neglecting to go to Confession at least once a year, are sins of omission. A. Actual sin is any willful thought, word, deed, or omission contrary to the law of God. A. Mortal sin is a grievous offense against the law of God. This sin is called mortal because it deprives us of spiritual life, which is sanctifying grace, and brings everlasting death and damnation on the soul.