I believe that it's not called anything, it is just a symbol to indicate that the angle is a right angle (90 degrees)
90 degrees
vertex angle
vertex
A Vertex is the point of intersection, and a Perpendicular Vertex is a vertex with all 90 degree angles, to be specific.
A segment.
90 degrees
sides
90 degrees
It has usually a red box at the vertex and is called a "right angle."
vertex angle
vertex
endpointendpointIt is called an apexvertex, plural verticesVertexA vertex.It is a vertex.
there are 4 vertices(singular vertex) of a square. the pointed edges are called vertex
The rays are called sides and the common endpoint is called vertex.
A Vertex is the point of intersection, and a Perpendicular Vertex is a vertex with all 90 degree angles, to be specific.
I don't know what a tessellation vertex is but I will try to Answer it I think it means the endpoint of a vertex which is also called vertices,which is the pointy ends of the vertex.
I think you mean corner and it's called a vertex. If you have more than one vertex they are called vertices.