Dimensional regularization
In theoretical physics, dimensional regularization is a particular way to get rid of infinities that occur when one evaluates Feynman diagrams in quantum field theory. One assumes that the spacetime dimension is not four but rather d which is thought of as a complex number. It often turns out that the integrals extrapolated to a general dimension converge. The divergences are then parameterized as quantities proportional to 1 / ε whose coefficients must be cancelled by renormalization to obtain physical quantities.