five-month-old

The compound "five-month-old" is a modern English construction built from three native Germanic elements. The numeral "five" traces back to the Proto-Indo-European root penkwe-, which gave rise to its equivalents across Indo-European languages. "Month" originates from a Germanic base related to the moon, reflecting the lunar basis of early timekeeping. "Old," a fundamental adjective for age, stems from the Proto-Germanic aldaz. The logic of the compound is transparent and arithmetic: it combines a number, a standard unit of temporal measurement, and a state-of-being suffix to precisely denote an age of five months, a pattern productive in English for specifying ages (e.g., "three-year-old").

Structure: five (5) + month (unit of time) + old (having existed for a specified time) - five: From Old English 'fīf', of Germanic origin; related to Dutch 'vijf' and German 'fünf', from an Indo-European root shared by Latin 'quinque' and Greek 'pente'. Functions as a cardinal number. - month: From Old English 'mōnath', of Germanic origin; related to Dutch 'maand' and German 'Monat', also to the moon. Functions as a noun denoting a unit of time. - old: From Old English 'eald', of Germanic origin; related to Dutch 'oud' and German 'alt'. Functions as an adjective describing age or duration.