'Empire' in the Bible

In every matter of wisdom and insight the king asked them about, he found them to be ten times better than any of the magicians and astrologers that were in his entire empire.

In the first year of Darius son of Ahasuerus, who was of Median descent and who had been appointed king over the Babylonian empire --

Then the king of the north will advance against the empire of the king of the south, but will withdraw to his own land.