%0 Journal Article %T Density in Approximation Theory %A Allan Pinkus %J Surveys in Approximation Theory %D 2005 %I %X Approximation theory is concerned with the ability to approximate functions by simpler and more easily calculated functions. The first question we ask in approximation theory concerns the possibility of approximation. Is the given family of functions from which we plan to approximate dense in the set of functions we wish to approximate? In this work, we survey some of the main density results and density methods. %U http://www.math.technion.ac.il/sat/papers/1/