The difference of two numbers 
and 
is 
,
where the minus sign denotes subtraction.
Difference
See also
Backward Difference, Finite Difference, Forward Difference, Minus, Subtraction, Symmetric DifferenceExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Difference." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Difference.html