A function 
is said to be strictly decreasing on an interval 
if 
for all 
,
where 
.
On the other hand, if 
for all 
, the function is said to be (nonstrictly) decreasing.
Strictly Decreasing Function
See also
Decreasing Function, Derivative, Nondecreasing Function, Nonincreasing Function, Strictly Increasing FunctionExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Strictly Decreasing Function." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/StrictlyDecreasingFunction.html