basileia

At its core this word names ruling itself, not a place on a map. It is what a king does and the authority by which he does it. The same word can describe a man traveling abroad to be granted royal power, or God exercising his sovereign rule over all things.

The Gospels use this sense most often in the phrase translated "kingdom of God" or "kingdom of heaven". Jesus announces that God's reign is arriving, that it is near, that people may enter it or be shut out of it. The point is not chiefly a territory but God actively taking up his rule, which is why the phrase sits beside the petition let your will be done, and why the reign can be said to come, to be among people, or to be received like a gift. This is the long-standing center of how scholars read the phrase, though they now stress that it never fully sheds the idea of a people and an order God reigns over.

The same kingship can be conferred on a human or messianic ruler.

• A nobleman goes to a far country to receive royal power and return
• Jesus confers a reign on his followers as his Father conferred one on him
• the Son is hailed with an everlasting throne

Here the word still means authority to rule, not the ground that is ruled.

The same word can shift from the act of ruling to the thing ruled: the territory, the subjects, the organized state under a king. This is the ordinary political sense familiar from everyday speech, where one kingdom can rise against another or be split by civil war.

The New Testament uses it this way for earthly powers.

• The tempter shows Jesus all the kingdoms of the world
• a divided kingdom cannot stand
• Herod offers up to half his kingdom
• by faith people conquered kingdoms

The line between this realm sense and the reign sense is not always sharp, since to rule is always to rule something, and many verses hold both ideas together. But where the stress falls on a bounded domain rather than on the exercise of authority, this is the sense in view.