diff --git a/Doc/lib/libstring.tex b/Doc/lib/libstring.tex
index b3699010169..897e5ea892f 100644
--- a/Doc/lib/libstring.tex
+++ b/Doc/lib/libstring.tex
@@ -135,7 +135,7 @@ The functions defined in this module are:
 \end{funcdesc}
 
 \begin{funcdesc}{capitalize}{word}
-  Capitalize the first character of the argument.
+  Return a copy of \var{word} with only its first character capitalized.
 \end{funcdesc}
 
 \begin{funcdesc}{capwords}{s}