one-month

The compound adjective 'one-month' is a straightforward combination of two native English elements. 'One' derives from the Proto-Germanic 'ainaz', which has cognates across Germanic languages and is ultimately from the Proto-Indo-European root 'oi-no-', meaning "one, single". 'Month' originates from the Proto-Germanic 'mēnōþs', related to 'mēnô' (moon), reflecting the ancient method of timekeeping by lunar cycles. The compound follows the common English pattern of numeral-noun hyphenation to form a phrasal adjective, where 'one' specifies the quantity of the temporal unit 'month', directly and logically describing a duration.

Structure: one (numeral) + month (noun) - one: From Old English 'ān', meaning "one, single, alone". It functions as a numeral modifier. - month: From Old English 'mōnaþ', meaning "month". It functions as the core noun being modified.