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 Ri (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]
R(i) or R[i]
See also index, array.