# Theorem/remark/proposition/etc tagging/labelling

I have been wondering this for years, and never really had so much trouble that I couldn't bear not to know, but now I think I'll just ask and see if anyone knows.

It is common practice to label one's theorems, corollaries, remarks, etc, and then later type "as per Theorem \ref{theoremname}...", but what I want to know is if I can label my theorem so that I can just type "as per \ref{whatever}", and the reference tag will automatically use "Theorem 6.1" or whatever.

My reason is that I just upgraded a remark to a corollary, and even though the remark is labelled, I now have to find the references to that remark and change them from "Remark \ref{tag}" to "Corollary \ref{tag}". Not a terribly recurring inconvenience, but just one of those things I'd like to know.

• Welcome to TeX.SX! You may have a look on our starter guide. About your question: you should have a look at the cleveref package. – jub0bs May 15 '13 at 13:57
• \thref of the package ntheorem provides exactly that feature. In addition to that, it works better with the hyperref package because the "Theorem 6.1" becomes clickable instead of just "6.1". – papabravo May 15 '13 at 14:16
• One may also hack fancyref, I've used that sucessfully for a few books. It depends on label prefixing though, instead of looking at the context of the \label. IMO a package like cleveref mess with a bit too much for my taste. – daleif May 15 '13 at 14:41

I use the fncylab package for this, which allows you to associate a macro expansion with every counter so that \ref{<label>} produces something more than just the value of the counter to which <label> corresponds. For example,

\usepackage{fncylab}
\labelformat{theorem}{Theorem #1}


does exactly what you want. I also tend to do \labelformat{equation}{(#1)} so that I don't have to bother with \eqref and, as a bonus, when used with hyperref, the entire (<number>) is hyperlinked rather than just the number.

The cleveref really helps to address this issue.

We see in Theorem \ref{thm:bigimportantthm}

you simply use

We see in \cref{thm:bigimportantthm}

In your preamble, you tell the package how you want it to behave- in this example, you might write

% each of the following has two versions
%   \crefname{environmentname}{singular}{plural}, to be used mid-sentence
%   \Crefname{environmentname}{singular}{plural}, to be used at the beginning of a sentence
\crefname{theorem}{thm}{thms}
\Crefname{table}{Thms}{Thms}


You can easily get it working with the hyperref and varioref as detailed in Difference between ref, varioref and cleveref. Decision for a thesis