order language as it takes
&gt; &gt; ;; first-order predicates as arguments.  Furthermore, it also takes
&gt; &gt; ;; numerals as arguments, which are not part of first-order languages
&gt; &gt; ;; generally.  However, it can be understood formally as an abbreviation
&gt; &gt; ;; as follows.
&gt; &gt; ;;
&gt; &gt; ;; Let REL be any n-place predicate, and let M be the numeral
&gt; &gt; ;; for the positive integer m, where m is less than or equal to n.
&gt; &gt; ;; Then we let
&gt; &gt; ;;
&gt; &gt; ;;   (nth