There are often differences between the exact analytical solution of the modeled differential equations (see Equation 11–1), and the fully converged solution of their discrete representations (see Equation 11–4). These differences are referred to as discretization errors.

Like the principal variables being solved for, errors in these values are both generated by localized sources and propagated (that is, amplified, advected, diffused) throughout the solution domain. Localized sources of error result from the high-order terms that are excluded from the discrete approximations of terms in the modeled equations. Conversely, error propagation results from the form of the terms that are included in the discrete approximations. Both error sources and propagation are affected by the solution and mesh distributions, as discussed in Controlling Error Sources and Controlling Error Propagation.