Sin

Literally it means missing the mark. Originally it was an archery term. If someone did not get a Bull’s-eye they “sinned”. Eventually it was used as a metaphor in life. A current definition might be “dysfunctional coping skills”, "bad habits" or making "poor choices". 

 When we set goals and fall short of those intentions we have “sinned” against ourselves.  If we mistreat people, hurt them or don't follow through on a promise we have “sinned” against them. When we don't do what God wants of us we have sinned against God. IN all of these situations we have missed the mark or the goal.

The goal God has for us is to “love God & Love one another” all of the other expectations that God has of us is filtered thru love. Even if we "follow the rules" perfectly but do it in an unloving manner we have still missed the primary goal of love, therefore we have sinned.

 The meaning is probably closer to “making a mistake” then the way it is often used in our culture: Evil. Evil is also missing the mark or goal of Love, but it is a sub-class within the categories of “sin”.  The word sin is a more general term that includes EVERY misdeed minor or big and even horrible.