Indexmenge
Indexmenge, in mathematics, is the German term for index set. An index set I is a set whose elements label members of a family of objects {A_i} or similar, with i ranging over I. The index set itself is just a set and need not carry extra structure, though in many contexts it has additional features such as an order or a directed structure.
In a typical situation, one writes a family of objects indexed by I as {A_i | i ∈ I}.
The index set is central to operations such as summation or product over a family: ∑_{i∈I} a_i
Index sets can be finite, countable, or uncountable, and they may be ordered or unordered depending on