The city has a ring to it. When you say the city in London, whether you know it or not, you are referring to a one square mile area with markers outlining the boundary. Everything outside of that is somewhere else other than the City of London. Buckingham Palace is not in the City of London. The Houses of Parliament and Big Ben are in the City of Westminster.
What constitutes a city is hard to define. Where I come from, the U.K., in order to be considered a city a place had to have a collection of urban development, a university, and a cathedral.
Now I live in the U.S. and if that were the defining criteria here, the U.S. would have a total of 267 cities which is clearly wrong; there are thousands of cities in the U.S.
Trying to decide in the modern USA what constitutes a city is hard. There are different criteria which might make a place constitute a city. In the U.S. cities are incorporated, which means it has a charter granted by the state. That seems straightforward, but in California, the terms city and town are explicitly interchangeable and made so by law.
Yet anyone thinking of the sprawling mass of Los Angeles, a city 44 miles long and 29 miles wide with a population of 3.976 million, would never compare it with Parker, a city located in Pennsylvania which had a population of 810 in 2010 and a total area of 1.1 square miles.
The population is one way in which a city could be categorized. To be a city in Japan, there has to be a population of 30,000. For the record, a megalopolis has more than ten million people – and there are plenty of those. Tokyo-Yokohama has a mind-boggling 37.8 million people and sits at the top spot, while Kolkata at number 20 has a minor 14.6. (U.S. cities in the top 20 are Los Angeles and New York, only.)
Conceptually economics might make sense. A city relies on a rural population and economy to feed it. There is a culture of fiscal exchange for goods and services aimed at supporting the population and not necessarily producing anything.
This could be why cities which were dependent on a single industry stopped flourishing when the industry dried up. Think of Detroit, desolated when the car industry abandoned it and now only just beginning to see some beginnings of urban renewal – yet it never lost its status as a city. So, cities can be bankrupt.
We could define a city as needing to have an element of government within its boundaries. This may work. If Federal, state and local government exist in a place which has a charter it could constitute a city. Most places will have some local or even state government, so this cannot count.
A better definition
For me, a sociologist and writer might have been the person who defined it the very best. A city, he said, was a place to meet strangers.