Subscripts help distinguish between similar elements or variables in equations. The oxygen molecule O2 has two oxygen atoms, represented by the subscript '2'.
Pro Tip 2/3
Sequential References
In sequences or lists, subscripts are used to reference elements in order. For a series a1, a2, a3..., the subscript indicates the position in the sequence.
Pro Tip 3/3
Chemical Formulas
Chemistry uses subscripts to show the number of atoms in a molecule. Water (H2O) has two hydrogen atoms, shown by the subscript '2'.