days-old

The compound adjective 'days-old' is a modern English formation following a productive pattern for specifying age or duration. It combines the plural noun 'days', derived from the Proto-Germanic 'dagaz', with the adjective 'old', from Proto-Germanic 'aldaz'. The construction is logically transparent, directly quantifying the age of a subject in terms of days. This pattern mirrors similar compounds like 'years-old' or 'hours-old', providing a concise and precise alternative to the more verbose phrasal form "X days old."

Structure: days (plural noun) + old (adjective) - days: From Old English 'dagas', plural of 'dæg' (day). A unit of time of 24 hours. In this compound, it functions as a quantifying noun. - old: From Old English 'ald', 'eald' (aged, ancient, of long existence). In this compound, it functions as the core descriptive adjective.