What makes a place urban?

We argue that “urbanity” is a function of population concentration. Empirically, this means urbanity can be measured along a spectrum, with increased population concentration in a place denoting increased urbanity. Phenomenologically, large concentrations of people in space—or mass corporeal co-presence—generates the essentially “urban” experience of living surrounded by the bodies and minds of strangers. We use a series of thought experiments to demonstrate the conceptual limitations of other historically common definitions of urbanity, such as the economic structure of a community, the presence of physical infrastructure, the political or administrative status of a geographic unit, or the degree of connectivity between people. These are not essential urban characteristics, but rather common epiphenomena associated with places that have large, spatially concentrated populations. A density-based definition does not require a settlement to be permanent, allowing for ephemeral urbanity (dense but temporary settlements). While density-based approaches to classifying human settlements based on gridded population data are conceptually robust, such as the methodology adopted by the United Nations in 2020 for cross-national comparison, we present an alternative measurement approach that is more closely aligned with our phenomenological understanding of urbanity.