Sin

All unrighteousness is sin:

1 John 5:17 

All wrongdoing is sin, and there is sin that does not lead to death.

Transgression of law is sin:

1 John 3:4 

Everyone who sins breaks the law; in fact, sin is lawlessness.

What is not of faith is sin:

Romans 14:23 

But the man who has doubts is condemned if he eats, because his eating is not from faith; and everything that does not come from faith is sin.

John 3:16 

“For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.

John 3:18 

Whoever believes in him is not condemned, but whoever does not believe stands condemned already because he has not believed in the name of God's one and only Son.

Not doing good when one knows to do good is sin:

James 4:17 

Anyone, then, who knows the good he ought to do and doesn't do it, sins.

Luke 12:48 

But the one who does not know and does things deserving punishment will be beaten with few blows. From everyone who has been given much, much will be demanded; and from the one who has been entrusted with much, much more will be asked.

What separates man from God is sin:

Isaiah 59:2 

But your iniquities have separated you from your God; your sins have hidden his face from you, so that he will not hear.

Proverbs 21:23 

He who guards his mouth and his tongue keeps himself from calamity.