I’m sorry, but while the simple answer to your question is "No, it doesn't", in fact there are so many ways to answer your question about δέκα and δεκάς. [Please ignore those that are not relevant to what you had in mind (perhaps all of them)];
If your question is about the origin of the English word “decade” and you wanted to translate that idea into Greek, then perhaps the words δεκαετία ἡ [δekaetía] χρονικὸν διάστημα ἤτοι (“viz.” not “whether”) περίοδος δέκα ἐτῶν. or the word δεκαετής -ές [δekaetís] ἐπίθετον ὃ διαρκεῖ δέκα ἔτη.(Using ἤτοι here in this way implies that in regard to Romans 6:16 I think that the dictionary meaning “whether” is a convenient rendering for the sake of translating that verse into English, rather than the “real” meaning of the word. I think that ἤτοι is a synonym of δηλαδὴ (i.e.) rather than the natural antecedent of ἢ).
If your question is about tithing, I suggest you look further down the page at the word δέκατος. (Perhaps you are forming the adjective in a non-standard way).
If your question is a general one about the Greek language, then the meaning for the word δεκάς ἡ [δekáδa] 1. σύνολον ἀποτελεῖται ἀπὸ δέκα μονάδων: 2. ὁμάς δέκα ὁμοίων προσώπων ἢ πραγμάτων. is a subset of the meanings for the word δέκα [δéka] 1. ἐπίθετον ὃ δηλοῖ ἓν σύνολον ἐκ δέκα (10) μονάδων. 2. (ὡς οὐσιαστικὸν.) τὸ δέκα: ὁ ἀριθμὸς καὶ τὸ γεγραμμένον σύμβολόν αὐτοῦ (δηλαδὴ τὸ<< ι’>> ἢ 10). Here, the main difference between the two is that δεκάς only functions as a noun (an abstract sor of one), whereas δέκα can function as either a noun or an adjective. I would expect to find δεκάς in philosophical texts not in texts written in a popular style.
If you are asking whether the NT has proto-Gnostic influences, then I think that the fact that we don’t see these –ά(δ)ς forms for numerals is slightly significant. They are more frequent in Gnostic or other cosmogonic / theogonic texts. If you are asking a question like this, then perhaps you could ask about (οἱ) δώδεκα which are never referred to as ἡ δωδεκάς. The apostles were real people and individuals. The NT is written in a more bare-knuckles style of Greek than the abstract philosophical style of texts where the –ά(δ)ς forms are likely to occur.
BA (Greek & Modern Greek), BTh, MA (Egyptology)
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