For a true understanding of the new Testament, it is essential that the "Word of Truth" should be "rightly divided" (2nd Timothy 2:15) as to the various usages of the word "kingdom" in all the different combinations and contexts in which we find it.
Each has its own peculiar and particular sense, which must not be confused with another.
As to the word basileia, it denotes sovereignty, which requires the actual presence of a sovereign, or king. There can be no kingdom apart from a king. We all know of countries which were once "kingdoms" but are now "republics", for the simple but sufficient reason that they have no "king", but are governed by the "public", which is sovereign.
The countries remain the same, have the same peoples, the same cities, the same mountains and rivers, but they are no longer kingdoms.
The common practice of taking the Kingdom as meaning the Church (See The "Kingdom" & The "Church"), has been the source of incalculable misunderstanding; and not "trying the things that differ" (Philippians 1:10) has led to great confusion in the interpretation of the whole of the New Testament.
The following definitions may help towards a clearer view of many important passages :--
It is the dispensational term; and is used sometimes of Messiah's Kingdom on earth, and sometimes of the heavenly sovereignty over the earth. It is not from or out of (Greek ek, Prepositions. vii) "this world" (Greek kosmos The Synonymous Words for "World", "Earth", etc. 1). This sovereignty comes from heaven, because the King is to come from thence (John 18:36). It was to this end He was born, and this was the first subject of His ministry (see The Fourfold Ministry of Our Lord). That Kingdom (Matthew 4:17, etc.) was rejected, as was also the further proclamation of it in Acts 3:19-26 (according to the prophetic parable of Matthew 22:2-7). Thenceforth the earthly realization of this Kingdom was postponed, and is now in abeyance until the King shall be sent from heaven (Acts 3:20). The "secrets" of this Kingdom (Matthew 13:11) pertained to the postponement of its earthly realization, on account of its being rejected.
These two would have had their realization even then, had Israel repented at the summons of the Lord, and of "them that heard Him" in Acts 3:19-26. In that case the later revelation of the "Mystery" (or the great secret) which, with its exanastasis and its "heavenward Call" (Philippians 3:11, 14), was hidden in God, would have remained in the keeping of the Father's Divine sovereignty.
This sovereignty had been "kept secret" (Romans 16:25), "hid in God" (Ephesians 3:9), "hid from ages and from generations" (Colossians 1:25); but after the Kingdom (No. 4) proclaimed by the Lord and by "them that heard Him" (Hebrews 2:4) had been postponed, it was revealed and "made known" (Ephesians 3) for the "obedience of faith" (Romans 16:26). The subjects of this Divine sovereignty, on their believing this subsequent revelation, are "sealed" (or designated) for their inheritance, which is to be enjoyed with Christ (Ephesians 1:13).
This relates to the position of those who come under that sovereignty.
At the end of the thousand years, No. 1, and perhaps others of them will cease, and be absorbed in the Kingdom of God (No. 2).