six-decade

The compound adjective 'six-decade' is a modern English formation that transparently combines two numerical and temporal concepts. The first element, 'six', originates from the Proto-Indo-European root s(w)eḱs, which gave rise to the number across many Indo-European languages, including Latin 'sex' and Greek 'hex'. The second element, 'decade', derives from the Greek 'dekas', based on 'deka' (ten), via Latin and French, specifically referring to a set or period of ten years. The compound's logic is purely multiplicative, literally meaning "six ten-year periods," and its formation follows the common English pattern of combining a number with a unit of time to create a specific durational adjective, such as 'two-day' or 'five-year'.

Structure: six (number) + decade (period of ten years) - six: From Old English 'siex', of Germanic origin; related to Dutch 'zes' and German 'sechs', from an Indo-European root shared by Latin 'sex' and Greek 'hex'. Functions as a cardinal number. - decade: From French 'décade', via Late Latin 'decas', from Greek 'dekas', from 'deka' meaning 'ten'. Functions as a noun denoting a period of ten years.