Premise: Istanbul ( [ ˌɪstænˈbʊl ] , [ - ˈbuːl ] or [ - stɑːn - ] İstanbul [ isˈtɑnbuɫ ] ) , historically known as Constantinople and Byzantium , is the most populous city in Turkey and the country 's economic , cultural , and historic center .
Hypothesis: Istanbul was formerly Constantinople.
Label: ENTAILMENT