Hendiadys (ἓν διὰ δυοῖν one by two) is the use of two words connected by a copulative conjunction to express a single complex idea; especially two substantives instead of one substantive and an adjective or attributive genitive.
χρόνῳ καὶ πολιορκίᾳ by length of time and siege = by a long siege 19.123, ἐν ἁλὶ κῡ́μασί τε
in the waves of the sea Hel. 226, ἀσπίδων τε καὶ στρατοῦ = ὡπλισμένου στρατοῦ
armed force El. 36.