[计] 可交换性

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.
[GG]

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
[GG]