The meaning of “οὖν”

“And his sisters, are they not all with us? Whence then hath this man all these things?”

“And the keeper of the prison told this saying to Paul, The magistrates have sent to let you go: now therefore depart, and go in peace.”

“Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.”

“Furthermore then we beseech you, brethren, and exhort you by the Lord Jesus, that as ye have received of us how ye ought to walk and to please God, so ye would abound more and more.”

“If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron?”