Sin is evil deeds or anything that separates you from God.
Bible Sources:
Micah 3:4
Then they will cry out to the LORD, But He will not answer them Instead, He will hide His face from them at that time Because they have practiced evil deeds
Isaiah 59:2
But your iniquities have made a separation between you and your God, And your sins have hidden His face from you so that He does not hear.
1 Corinthians 15:17
And if Christ has not been raised, your faith is worthless; you are still in your sins.
Exodus 32:33
The LORD said to Moses, "Whoever has sinned against Me, I will blot him out of My book.