A subscript is a character or string that is smaller than the preceding text and sits at or below the baseline. Subscripts have many scientific applications, including mathematics, computer science, and chemistry.

Below is an example of a math function that uses subscripts to define the Fibonacci sequence:

Fn = Fn-1 + Fn−2

The small "n" is a subscript. When used in the context "Fn," it refers to a function evaluated for the value "n." The text n-1 and n-2 are also subscripts that define previous values of "n" in the sequence.

In computer science, subscripts can be used to specify a number system. For example, the decimal or "denary" number 200 is equal to 11001000 in binary and C8 in hexadecimal. Instead of writing out the full words, you could describe the equality of the three numbers with the following statement:

20010 = 110010002 = C816

Subscripts are also used in chemistry to describe chemical compounds. For example, the molecular structure of water, which includes two hydrogen atoms and one oxygen atom, is commonly written:


Most modern word processors include a text formatting option that allows you to enter subscript or superscript text. HTML provides the <sub> tag for displaying subscript on webpages. If a text editor doesn't provide subscript formatting, you can shrink the font size of the subscript as a workaround. If you are working with plain text, the only option is to enter subscript characters on a separate line below the text.

Updated May 14, 2015 by Per C.

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