What is "commutativity"

commutativity \com`mu*ta*tiv"i*ty\, n. (Math.) the property of a binary operation or operator such that the result of one term operating on a second is equal to the result of the second term operating on the first.

Note: If the symbol ``*'' is taken to be a commutative binary operator, then the following equation holds: a*b = b*a A common example is the addition operator for real numbers, ``+'': a+b = b+a

n. (context mathematics physics English) The state of being commutative.