Some people would say that the earliest use of a word provides the best clue to its definition (that is the principle behind the Oxford English Dictionary). The earliest definition of sin in the Bible is found in the story of Cain and Abel. Here God defines sin:

So sin, in its most basic form, sin is when someone does not do what is right. It also has an independent influence on us, in that it tries to master us. "Jesus answered them, 'Most assuredly, I say to you, whoever commits sin is a slave of sin.'" (John 8:34 NKJV).

Sin is something that we all deal with. "For all have sinned, and come short of the glory of God" (Rom. 3:23 KJV). And the result of sin is death. "Then, when desire has conceived, it gives birth to sin; and sin, when it is full-grown, brings forth death" (Jas. 1:15 NKJV).

God provides a remedy for sin. "But because of his great love for us, God, who is rich in mercy, made us alive with Christ even when we were dead in transgressions—it is by grace you have been saved" (Eph. 2:4-5 NIV).

The remedy for sin that God provides allows our relationship to be restored with God.

Jesus told us that there is only one way to obtain forgivness for sin. "Jesus answered, 'I am the way and the truth and the life. No one comes to the Father except through me.'" (John 14:6 NIV).