/ ɪmˈpɪəriəl; NAmE -ˈpɪr-/ adjective [ only before noun ]
1.
connected with an empire :
he imperial family / palace / army
imperial power / expansion
2.
connected with the system for measuring length, weight and volume using pounds, inches, etc.
—compare metric
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WORD ORIGIN
late Middle English : via Old French from Latin imperialis , from imperium command, authority, empire; related to imperare to command. Compare with emperor , empire , also with imperious .