-each abbreviation. The symbol's name is the abbreviation; its value is
-the expansion; its function definition is the hook function to do the
-expansion (@pxref{Defining Abbrevs}); its property list cell contains
-the use count, the number of times the abbreviation has been expanded.
-Because these symbols are not interned in the usual obarray, they will
-never appear as the result of reading a Lisp expression; in fact,
-normally they are never used except by the code that handles abbrevs.
-Therefore, it is safe to use them in an extremely nonstandard way.
-@xref{Creating Symbols}.
+each abbreviation. The symbol's name is the abbreviation; its value
+is the expansion; its function definition is the hook function to do
+the expansion (@pxref{Defining Abbrevs}); its property list cell
+typically contains the use count, the number of times the abbreviation
+has been expanded. Alternatively, the use count is on the
+@code{count} property and the system-abbrev flag is on the
+@code{system-type} property. Abbrevs with a non-@code{nil}
+@code{system-type} property are called ``system'' abbrevs. They are
+usually defined by modes or packages, instead of by the user, and are
+treated specially in certain respects.
+
+Because the symbols used for abbrevs are not interned in the usual
+obarray, they will never appear as the result of reading a Lisp
+expression; in fact, normally they are never used except by the code
+that handles abbrevs. Therefore, it is safe to use them in an
+extremely nonstandard way. @xref{Creating Symbols}.