The vertex of an isosceles triangle having angle different from the two equal angles is called the apex of the isosceles triangle.
The common polygon vertex at the top of a pyramid or the vertex of a cone is also called an apex.
Apex
See also
Apex GraphExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Apex." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Apex.html