Index

The word "index" has a very large number of completely different meanings in mathematics. Most commonly, it is used in the context of an index set, where it means a quantity which can take on a set of values and is used to designate one out of a number of possible values associated with this value. For example, the subscript i in the symbol a_i could be called the index of a.

In a radical RadicalBox[x, n], the quantity n is called the index.

The word index has a special meaning in economics, where it refers to a single quantity used to quantify the "average" value of a possibly complicated set of quantities. In this context, it is sometimes called an index number.

In topology, index theory refers to the study of topological invariants of manifolds.

See also

Family, Index Gymnastics, Index Lowering, Index Number, Index Raising, Index Set, Manifold, Multi-Index Notation, Multiplicative Order

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Cite this as:

Weisstein, Eric W. "Index." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Index.html

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