Subscripts are commonly used in chemical formulas. A scientist would write the formula for water, H2O, so that the 2 appears lower and smaller than the letters on either side of it. That's what subscript is for, to set certain characters apart from others.

Why do we superscript words?

A superscript or subscript is a number, figure, symbol, or indicator that is smaller than the normal line of type and is set slightly above it (superscript) or below it (subscript). ... If you're creating a footnote, you might also want to do this with a number.

What do subscripts represent?

Subscripts are important numbers in formulas, especially when you're trying to understand how many atoms of an element are present. A subscript is a number to the right and below the abbreviation of an element that indicates the number of elements that are present.