compound
\\[0ex]IsGroup($T$;${\it op}$;${\it id}$;${\it inv}$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$IsMonoid($T$;${\it op}$;${\it id}$) \& Inverse($T$;${\it op}$;${\it id}$;${\it inv}$)