Sin is ...
1. Sin is lawlessness
"Everyone who sins breaks the law; in fact, sin is lawlessness"
(1 John 3:4)
2. Sin is not believing in Jesus
"in regard to sin, because men do not believe in me"
(John 16:9)
3. Sin is knowing the good I ought to do and not doing it.
"Anyone, then, who knows the good he ought to do
and doesn't do it, sins" (James 4:17)
4. Sin is everything that does not come from faith.
"... everything that does not come from faith is sin" (Romans 14:23)