A book that I am reading defines the spherical sector as follows:
A spherical sector is a solid generated by rotating a sector of a circle about an axis which passes through the center of the circle but which contains no point inside the sector.
I understood most of the definition except for the part indicated by the bold letters. The way I visualized how the spherical sector is formed is like this:
Clearly, some points of the axis of rotation are contained within the sector, which contradicts the statement "but which contains no point inside the sector." Am I missing something here?