List

A list is a collection $S$ of elements stored in a certain linear order.

$$S:\{E_1,E_2,E_3,\dots ,E_i,\dots ,E_n\}$$

We can refer to the elements in $S$ as first, second, third, … The index of an element $e$ in $S$ is the number of elements before $e$ in $S$. The index can be used to specify where to insert a new element into the list, or where to remove an old element from.