In the simplest terms- God sets a standard and we miss this standard.  We miss the mark!  It is the barrier between God and us that separates us from our Lord Jesus.  What we are and what God intended us to be.  It is a condition or state that we are all in as well of an action or lack of action.  Sin is anything contrary to God and his character.

1 JOHN 3:4- EVERYONE WHO MAKES A PRACTICE OF SINNING ALSO PRACTICES LAWLESSNESS, SIN IS LAWLESSNESS.  

Any thought or activity bereft of God’s guidance and in violation of God’s law.  God has laws for his children regardless of being Jewish or a Gentile.  Don’t be confused with the law of the Old Testament.  Think of it as God’s way or the highway to death.  It is a question of life and death.