A subscript is a small number written below a letter or number, not above.

Here are some examples:

* H₂O (the 2 is a subscript indicating two hydrogen atoms)

* CO₂ (the 2 is a subscript indicating two oxygen atoms)

* x₁ (the 1 is a subscript indicating the first value of x)

Superscripts, on the other hand, are small numbers written above a letter or number.