Editing Index set (section)

==Examples==
*An [[enumeration]] of a set {{mvar|S}} gives an index set <math>J \sub \N</math>, where {{math|''f'' : ''J'' → ''S''}} is the particular enumeration of {{math|''S''}}.
*Any [[countably infinite]] set can be (injectively) indexed by the set of [[natural numbers]] <math>\N</math>.
*For <math>r \in \R</math>, the [[indicator function]] on {{math|''r''}} is the function <math>\mathbf{1}_r\colon \R \to \{0,1\}</math> given by <math display="block">\mathbf{1}_r (x) := \begin{cases} 0, & \mbox{if } x \ne r \\ 1, & \mbox{if } x = r. \end{cases} </math>

The set of all such indicator functions, <math>\{ \mathbf{1}_r \}_{r\in\R}</math>, is an [[uncountable set]] indexed by <math>\mathbb{R}</math>.