  Though crime is linked to different socio-economic factors, it exhibits
remarkable regularities regardless of cities' particularities. In this chapter,
we consider two fundamental regularities in crime regarding two essential
aspects of criminal activity: time and space. For more than one century, we
know that (1) crime occurs unevenly within a city and (2) crime peaks during
specific times of the year. Here we describe the tendency of crime to
concentrate spatially and to exhibit temporal regularities. We examine these
phenomena from the complex-system perspective of cities, accounting for the
possibility of both spatial heterogeneity and non-stationarity in urban
phenomena.
