Английский разговорный словарь (основной) - septenary
Septenary
septenary
sepˈtenərɪ adj. & n. --adj. of seven, by sevens, on thebasis of seven. --n. (pl. -ies) 1 a group or set of seven (esp. years). 2 a septenarius. [L septenarius (as SEPTENARIUS)]