# residual

A subspace $A$ of a topological space $X$ is called residual (or comeager) if and only if it is second category and its complement $X\setminus A$ is first category. Equivalently, a set is residual if and only if it contains a countable intersection of open (http://planetmath.org/OpenSet) dense sets.

Title residual Residual 2013-03-22 13:04:05 2013-03-22 13:04:05 mps (409) mps (409) 7 mps (409) Definition msc 54E52 BaireCategoryTheorem SardsTheorem comeager