chapter  I
6 Pages


Y ∈ I . As an example, let S be the set N of natural

numbers and let I be the set of all finite subsets of N. Then I is an ideal on S.

identification map A continuous onto mapping f : X → Y such that the topology on Y is the identification topology; that is, U is open in Y if and only if f−1(U) is open in X. See also quotient map.