In HTML the <sub> tag is used to arrange a text as a subscript. Subscripts are rendered with a reduced baseline and smaller text.


Example:

<!DOCTYPE html>
<html>
    <head>
        <title>Page Title</title>
    </head>
    <body>
        <p>a<sub>2</sub>+ b<sub>2</sub></p>
    </body>
</html>


output: