Definitions [7]
A conic section is the locus of a point such that the ratio of its distance from a fixed point (focus) to a fixed line (directrix) is constant.
The point which bisects every chord of the conic passing through it is called the centre of the conic section.
The straight line passing through the focus and perpendicular to the directrix is called the axis of the conic section.
The points of intersection of the conic section and the axis are called the vertices of the conic section.
The chord passing through the focus and perpendicular to the axis is called the latus rectum of the conic section.
A chord of a conic passing through the focus is called a focal chord.
A straight line drawn perpendicular to the axis and terminating at both ends of the curve is a double ordinate of the conic section.
Formulae [1]
$$e = \frac{\text{distance from focus}}{\text{distance from directrix}}$$
