短语词组短语syntactic monoid 语法幺半群monoid closure [数]独异点闭包regular monoid 正则幺半群small monoid 小幺半群Algebraic Monoid 代数么半群lattice monoid 格半群Monoid congruence 幺半群clifford monoid clifford 半群inverse monoid 逆半群 返回 monoid