In geometry, a cone is a three-dimensional figure, that tapers smoothly from a flat base, usually a circle, to a point not contained in the base. This point is called apex or vertex.
A cone with a circle as its base, is called circular. It is right circular if the axis, the straight line passing through the middle point of the circle base, is perpendicular to the circle base. Otherwise, it is referred to as an oblique circular cone.
In topology, this idea is generalized. For a topological space \(X\), we call \(CX:=X\times [0,1]/X\times \{0\}\) cone on \(X\), where \(C\) is obtained by collapsing \(X\times \{0\}\) to a point .