What is sin?

I cannot improve upon the definition of sin found in the Westminster Shorter Catechism 14, “Sin is any want of conformity unto or transgression of the law of God.” We are all those who have missed the mark. In the words of Apostle Paul, “All have sinned and fall short of the glory of God” (Rom. 3:23). In our sin, we rebel against God’s glory and Lordship over us.  But, as Paul puts it in 2 Corinthians 5:21, “For our sake [God] made him [Christ] to be sin who knew no sin, so that in him we might become the righteousness of God.”