in Geometry and Conic Sections, is applied to a certain point in the parabola, ellipse, and hyperbola, where the rays reflected from all parts of these curves meet. In Optics, a point in which any number of rays meet, after being reflected or refracted.

FETUS, the young of viviparous animals whilst in the womb, and of oviparous animals before being hatched. See Anatomy, and Physiology.