36,formula_15是formula_1在formula_11下的幺元。则：
零元.设formula_11: formula_12是集合formula_1上的二元运算，formula_65，则：
零因子.设formula_11: formula_12是集合formula_1上的二元运算，formula_87且formula_88,formula_66是formula_1在formula_11下的零元。则：
交换律.设form