There exists an element denoted by 0 ∈ R {\displaystyle 0\in R} such that a + 0 = a {\displaystyle a+0=a} .
Існуе элемент 0 ∈ K {\displaystyle 0\in K} такі, што 0 + a = a {\displaystyle 0+a=a} (нейтральны элемент)