The first derivative of a function 
is a single derivative of the
function, denoted 
.
The term "first derivative" is commonly used instead of just "derivative"
to distinguish it from higher-order derivatives. For example, specifying the order
of the derivative distinguishes between the first
derivative test and second derivative test.
First Derivative
See also
Derivative, First Derivative TestExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "First Derivative." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/FirstDerivative.html