Commutativity
From HandWiki
A property of algebraic operations (cf. Algebraic operation). For addition and multiplication, commutativity is expressed by the formulas
\begin{equation}
a+b=b+a,\quad \text{ and } \quad ab=ba.
\end{equation}
A binary operation $*$ is commutative (or, what is the same, satisfies the law of commutativity) if in the given algebraic system the identity $a*b=b*a$ holds.
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