Index (mathematics)

This is referring to Index in the concept of mathematics. For other uses, see Index.

In mathematics, an index is a superscript or subscript to a symbol. Superscript indices are often, but not always, used to indicate powers. Subscript indices are usually used to label a set or sequence of variables. See also index set.

The index of a subgroup is the number of its left cosets (which is equal to the number of its right cosets).

The index of a Fredholm operator is the dimension of its kernel minus the dimension of its cokernel.

The index of a real quadratic form Q is defined (but not always consistently) as p − q where Q can be written as a difference of p squared linear terms and qsquared linear terms.