seven-month-old

The compound "seven-month-old" is a modern English construct built from three fundamental, ancient roots. "Seven" descends from a nearly universal Indo-European numeral, while "month" is tied to the lunar cycle, reflecting early timekeeping. "Old" originates from a root concerning growth and nourishment. The compound's logic is transparent and arithmetic: it sequentially specifies a quantity of time units ("seven months") and then applies the state of having existed for that duration ("old"). This pattern creates a precise, hyphenated adjective or noun for describing age, a common and productive method in English for forming such terms.

Structure: seven (number) + month (time unit) + old (age) - seven: From Old English seofon, from Proto-Germanic sebun, from Proto-Indo-European septḿ̥. Functions as a cardinal number. - month: From Old English mōnaþ, from Proto-Germanic mēnōþs, related to mēnô ("moon"). Functions as a noun denoting a unit of time. - old: From Old English eald, from Proto-Germanic aldaz, from Proto-Indo-European h₂el- ("to grow, nourish"). Functions as an adjective describing age.