Projective cone

This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Projective cone" – news · newspapers · books · scholar · JSTOR (July 2012) (Learn how and when to remove this message)

A projective cone (or just cone) in projective geometry is the union of all lines that intersect a projective subspace R (the apex of the cone) and an arbitrary subset A (the basis) of some other subspace S, disjoint from R.

In the special case that R is a single point, S is a plane, and A is a conic section on S, the projective cone is a conical surface; hence the name.