Chicago is a city.
Chicago . Positioned along Lake Michigan , the city is an international hub for finance , commerce , industry , technology , telecommunications , and transportation : O'Hare International Airport is the second-busiest airport in the world when measured by aircraft traffic ; the region also has the largest number of U.S. highways and rail road freight . In 2012 , Chicago was listed as an alpha global city by the Globalization and World Cities Research Network , and ranked seventh in the world in the 2016 Global Cities Index .