Definition:Index


 * Set Theory:
 * Index: an element of an indexing set


 * Sequences:
 * Index: the index of a term $x_k$ of a sequence $\sequence {x_n}$ is $k$


 * Group Theory:
 * Index: order of coset space


 * Matrix Theory:
 * Index of Matrix Element: one of the two parameters which specifies an element of a matrix


 * Algebra and Analysis:
 * Power (Algebra): the $y$ term in expressions such as $x^y$, also known as the exponent of $x$
 * Index variable: the dummy variable $j$ in the summation $\ds \sum_{j \mathop = 1}^n a_j$


 * Statistics:
 * Index: A figure used to show the variation in a quantity over a period of time.