sub·script / ˈsəbˌskript/ • adj. (of a letter, figure, or symbol) written or printed below the line.• n. a subscript letter, figure, or symbol. ∎  Comput. a symbol (notionally written as a subscript but in practice usually not) used in a program, alone or with others, to specify one of the elements of an array.

subscript A means of referring to particular elements in an ordered collection of elements. For example, if R denotes such a collection of names then the ith name in the collection may be referenced by R_i (i.e. R subscript i). This printed form is the origin of the term but it is also used when the “subscript” is written on the same line, usually in parentheses or brackets: R(i) or R[i]

See also index, array.