Improve English

base/doc/ltnews37.tex

@@ -366,7 +366,7 @@ \subsection{Performance in checking file existence}
 The additon of hooks, etc., to file operations had a side-effect in that
 multiple checks were made that the file existed. In larger documents using
 lots of files, these filesystem operations caused non-trivial performance
-impact. We now cache the file seen status, such that these repeated filesystem
+impact. We now cache the existence of files, such that these repeated filesystem
 calls are avoided.
 
 \subsection{\pkg{doc}: Handle \texttt{\textbackslash\textvisiblespace} correctly in the index}