# Error with \textsubscript

I am seeing this in the body of the latex format for a journal I want to publish with. But it's prompting an error.

What does this mean `CO\textsubscript` and which package do I have to include to be able to use it?

In that case you need the `subscript` package: `\usepackage{subscript}`.
Another more comprehensive solution for pre-2015 distribution is the `fixltx2e` package (the elements of which are now incorporated into LaTeX itself).
Once the command is defined (by either package, or by an updated LaTeX core), you write `CO\textsubscript{2}` for carbon dioxide.
• how old had be `latex` that `\subscript{...}` is not defined? – Zarko Mar 9 '18 at 14:33