A morphism 
is said to be separable if 
is a separable extension
of 
.
Separable Morphism
See also
MorphismExplore with Wolfram|Alpha
References
Hartshorne, R. Algebraic Geometry. New York: Springer-Verlag, p. 300, 1977.Referenced on Wolfram|Alpha
Separable MorphismCite this as:
Weisstein, Eric W. "Separable Morphism." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SeparableMorphism.html