This question stems from something I stumbled across in the newtx package documentation:
2 Text mode options
…
If you use the babel package, you should load it before newtxtext—for example:
\usepackage[<babel options>]{babel} \usepackage[osf]{newtxtext}More generally, the pattern of the preamble should be:
<encoding options> [optional] \usepackage{substitutefont} % so you can change babel's fonts [optional] \usepackage[<babel options>]{babel} \usepackage[p,osf]{newtxtext}% osf in text, lining figures in math [optional] redefine the plain theorem style if necessary <other font loading commands> \usepackage{newtxmath} <substitutefont commands>
I don’t understand what this section is trying to get at – what does babel have to do with fonts?
Moreover, I was under the impression that the recommended package order was as follows:
\documentclass{…}
% optional font packages
% \usepackage{<font package>}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
% further packages
\begin{document}
…
See e. g. the babel documentation, fntguide, or this answer.
\substitutefonts, that's rarely necessary and doesn't directly depend onbabel. My preferred loading order isfontenc,babeland fonts. I see no reason to “redefine the plain theorem style” before loadingnewtxmath. – egreg Mar 24 '20 at 22:45% so you can change babel's fonts. As far as I understand, there’s no such thing as “babel’s fonts”. Also, before reading that paragraph, I had never heard of thesubstitutefontpackage (and I’m still not sure what its purpose is). – Socob Mar 25 '20 at 01:32