Sin: A working definition

In Greek - the word for "sin" is "amartia," which literally means "to miss the mark." For Christians, the "mark" for which we strive is to live in communion with God, basing our lives and actions on the life and actions of Jesus Christ; hence, when we "miss this mark" we sin.
Orthodox Christians believe that sin may be voluntary or involuntary and conscious or unconscious and that sin is always personal (moral) in nature, leaving each person to account for what he or she has done or left undone.