adj. 1. of or relating to a cone. 2. (as substantive) any expression that represents a conic section; any second degree equation. Thus is the general conic in Cartesian coordinates; it can also be expressed as where e is the eccentricity, (α, β) the focus, and px + qy + r is the equation of the directrix of the conic. In vertex form the equation is where 2p is the parameter of the conic, that is, the length of its latus rectum, which in the ellipse and hyperbola equals b²/a (where a and b are the lengths of the semi-axes of the conic), and ɛ is the numerical eccentricity, e/a; there are many other equivalent descriptions. This figure shows the graphs of these curves for specific values of ɛ, which is constant for any family of similar curves: 0 < ɛ < 1 for an ellipse; ɛ = 1 for a parabola; ɛ >1 for a hyperbola; and ɛ = 0 for a circle (when p is the radius). Lines and points are degenerate conics; in augmented Euclidean geometry all degenerate conics are pairs of lines or repeated lines, but in Euclidean geometry, points, for example, are determined by equations such as x² + y² = 0, and there are a large number of distinct cases.3. (as substantive) another word for conic section.