These words are typically translated sin, transgression, and iniquity. According to a classical understanding of these words, a sin is missing the mark. You were going in the right direction, but you veered or fell short. A transgression is going astray. You had good intentions, but you took the wrong path.
Iniquity is much more serious.
New Testament Greek has a similar construct of these words. As I studied the passage in question I was struck at how little information my Protestant scholars provided on the subject. A mortal sin is one that causes damnation, while a venial sin does not. The list of mortal sins, according to the Catholic Church, mostly has to do with church law. This means the sin must be completely out of line with the commandments to love and honor God.