  Nuclear density functional theory (DFT) is the only microscopic, global
approach to the structure of atomic nuclei. It is used in numerous
applications, from determining the limits of stability to gaining a deep
understanding of the formation of elements in the universe or the mechanisms
that power stars and reactors. The predictive power of the theory depends on
the amount of physics embedded in the energy density functional as well as on
efficient ways to determine a small number of free parameters and solve the DFT
equations. In this article, we discuss the various sources of uncertainties and
errors encountered in DFT and possible methods to quantify these uncertainties
in a rigorous manner.
