Concept

# Index

Sometimes instead of using different variables for different values, an index is used with the same variable. To distinguish between values, the index is written as a subscript to the term.

For example, indices can be used to specify multiple solutions of an equation, $x_1$ and $x_2.$ Another case is a sequence with unknown terms, which is often written as $a_1, \ a_2, \ a_3, \ldots, \, a_n.$ One could write these as $a$, $b$, $c,$ etc .. but since a infinite amount of letters exist, writing them with an index can be a good option.