I want to write so much and there is so little space . . . on verses in Greek about the kingdom of God. But for a start here is Luke 17:21.
οὐδε ἐρουσιν ἰδου ὡδε ἠ ἰδου ἐκει, ἰδου γαρ ἡ βασιλεια του Θεου ἐντος ὑμων ἐστιν.
οὐδε - but not (or possibly and not)
ἐρουσιν - they say
ἰδου - look (imperative) sometimes translated 'behold' or 'lo'
ὡδε - here
ἠ - or
ἰδου - look (imperative)
ἐκει - there
so far - but not they say look here or look there
Let me try to put that into better English - but they do not say, "Look here!" or, "Look there!"
It's interesting that this is often translated in the future tense, but I see no indication of future in the Greek.
ἰδου - look
γαρ - for or because (timid word, should be at the beginning of the clause, but has moved)
ἡ βασιλεια - the kingdom
του Θεου - of the God. The 'of' is denoted by the genitive case. Proper nouns in Greek often have the article.
ἐντος - inside. This is, I think, a stronger preposition than just in (ἐν). It is also used in the NT in the context of inside a cup.
ὑμων - you (plural, genitive case as required after ἐντος)
ἐστιν - is (third person singular)
This part - for, look, the kingdom of God is inside you (pl).
The whole verse in my translation - But they do not say, "Look here!" or, "Look there!" for Look! The Kingdom of God is inside you.
When one bears in mind that this comes after verse 20 where Jesus tells the Pharisees that the kingdom of God does not come with 'observation', the important part of this verse seems to be that the coming of the kingdom is hidden because it is inside people.
Of course there are other verses that say more . . . but that will be another post.