% The "is a face of" and "is a proper face of" relations.
\newcommand*{\faceof}{ \trianglelefteq }
\newcommand*{\properfaceof}{ \triangleleft }
% The "is a face of" and "is a proper face of" relations.
\newcommand*{\faceof}{ \trianglelefteq }
\newcommand*{\properfaceof}{ \triangleleft }