In the United States, the Tenth Amendment leaves the organization of local government to the states rather than to the United States Government. Therefore, each state is free to define for itself the qualifications for a community to become a city and the powers that cities have.
In the United Kingdom traditionally a city was a town possessing a cathedral, all other large settlements being merely towns. This is, however, no longer the case; city status is conveyed by royal charter. Some towns have cathedrals but are not cities (e.g. Chelmsford, Guildford); others are cities but have no cathedral (e.g. Derby, Sunderland, Newport).