Matthew 24:14 wrote:Καὶ κηρυχθήσεται τοῦτο τὸ εὐαγγέλιον τῆς βασιλείας ἐν ὅλῃ τῇ οἰκουμένῃ εἰς μαρτύριον πᾶσιν τοῖς ἔθνεσιν· καὶ τότε ἥξει τὸ τέλος.
Matthew 28:20 wrote:διδάσκοντες αὐτοὺς τηρεῖν πάντα ὅσα ἐνετειλάμην ὑμῖν· καὶ ἰδού, ἐγὼ μεθ’ ὑμῶν εἰμι πάσας τὰς ἡμέρας ἕως τῆς συντελείας τοῦ αἰῶνος. Ἀμήν.
Wecome to Greek. You have come to the right language to look at deeper questions of understanding the text of New Testament and of the LXX.
Many people begin their interest in Greek in response to a claim that they have heard someone make about how to understand the meaning of a text or concept in the New Testament. Learning enough Greek to be able to make your own stand in whatever storms that might come is no easy thing. Exploring one particular point or theme exhaustively is good for one thing from one point of view, but not very flexible. It is like learning to drive from home to the supermarket and back in the dead of night in good conditions. Throw in a complication, or ask them to drive to anywhere other than the supermarket and they are lost.
It is much better to be a quiet poor driver capable of any and all reasonable situations than to be a robot-like expert in just one point. I'm encouraging you to get a rounded general knowledge in addition to the particular point that you are asking.
If I were reading καὶ τότε ἥξει τὸ τέλος in Matthew 24:14 and ἕως τῆς συντελείας τοῦ αἰῶνος in Matthew 28:20, I would look at τὸ τέλος and say that that "end" was capable of being the subject of a verb, so, it has the capacity to do or achieve something. The τὸ τέλος is expressed as something that is going to get something done, perhaps make a change.
That is different from the other "end" in the prepositional phrase ἕως (+ genitive of place [a boundary / border] or time [a point of time NOT a duration of time]) "until".
Do you know the meaning of the word αἰών [αἰών, -ῶνος, ὁ]? Well, it means "age", and that is a long period of time, viz. a duration of time. ἕως "until" is suitable for the words ἐγὼ μεθ’ ὑμῶν εἰμι "I am with you", but it would be strange to put ἕως "until" directly together with τοῦ αἰῶνος "age" because that is a long duration of time.
συντελεία, then performs a similar function in languge as "cup" does "in a cup of water". In English, there are countable and uncountable nouns, and ther are words that allow uncountable words to function conceptually as countable, eg. "head of cattle", "piece of cake", "glass of water". ἕως needs a boundary not an expanse, and συντελεία "changes" the (2D) expanse of αἰών to a (1D) boundary.
Vladislav Kotenko wrote:Can they refer to the same thing?
Perhaps, but they are not intentionally being equated in the text. "Swim to the shore" and "The shore supports a different ecosystem" could be said to be referring to the same "shore", but nobody would immediately put those together to say "moving through the water changes the ecosystem in which we operate", would they?
Vladislav Kotenko wrote:Do they have the same derivation?
I don't understand what you are asking.