A cone is an -dimensional geometric shape that tapers smoothly from a base (usually flat and circular) to a point called the apex or vertex.
Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base. The term "cone" is sometimes used to refer to the surface or the lateral surface of this solid figure (the lateral surface of a cone is equal to the surface minus the base).
The axis of a cone is the straight line (if any), passing through the apex, about which the base has a rotational symmetry.
In common usage in elementary geometry, cones are assumed to be right circular, where right means that the axis passes through the centre of the base (suitably defined) at right angles to its plane, and circular means that the base is a circle. Contrasted with right cones are oblique cones, in which the axis does not pass perpendicularly through the centre of the base. In general, however, the base may be any shape, and the apex may lie anywhere (though it is often assumed that the base is bounded and has finite area, and that the apex lies outside the plane of the base). For example, a pyramid is technically a cone with a polygonal base.