'Sin' in the Bible

Therefore I say unto you, Every sin and blasphemy shall be forgiven unto men; but the blasphemy against the Spirit shall not be forgiven.

And if thy brother sin against thee, go, show him his fault between thee and him alone: if he hear thee, thou hast gained thy brother.

Then came Peter and said to him, Lord, how oft shall my brother sin against me, and I forgive him? until seven times?