What is sin? Sin is anything that falls short of God's will. The easiest way to define it is by the Ten Commandments that God gave to Moses. You know, "Thou shalt, Thou shalt not." The first commandment, I am the Lord Your God...you will have no other gods before Me, simply means God must be first in everything. If He isn't the most important thing in your life and the first consideration in every choice you make, then you are sinning. By that standard, we all have sinned. We could talk about lying, disrespecting our parents, envy, lust, blasphemy...all of these and more are sins that are spoken of in the Ten Commandments.