decade-long

The compound adjective "decade-long" is a modern English formation that transparently combines two elements of ancient lineage to specify a duration. The first element, "decade," traces back to the Greek deka, meaning "ten," a numeral with a clear Proto-Indo-European root déḱm̥t. The second element, "long," originates from the Old English lang, describing extended spatial or temporal measure, derived from the Proto-Germanic langaz. The logic of the compound is straightforwardly mathematical and descriptive, fusing the classical concept of a ten-year unit with the Germanic concept of extended duration to create a precise term for a ten-year span.

Structure: decade (ten-year period) + long (having great duration) - decade: From Latin decas, from Greek dekas (a group of ten), from deka (ten). Functions as the quantifying element. - long: From Old English lang, long (having great linear extent or duration), from Proto-Germanic langaz. Functions as the descriptive element indicating duration.