A principal or chief city; a city that holds supreme importance or authority over others.
From Greek 'arch-' meaning chief or first, combined with 'city.' The prefix became productive in English from the 14th century onward to denote supremacy or primary importance.
This word never really caught on in English, but it reveals how medieval writers tried to create hierarchies of importance—even cities had their own pecking order, with some considered 'arch' or supreme over their neighbors.
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