Paraboloid

Part of speech: noun, adjective

Definitions

1. A three-dimensional surface generated by rotating a parabola around its axis of symmetry
2. A shape resembling a bowl or dish, defined mathematically by a specific quadratic equation
3. A geometric structure that exhibits reflective properties, often used in satellite dishes and telescopes to focus signals or light

Etymology: The name is a compound built from "parabola" and the suffix "-oid". "Parabola" comes from Ancient Greek "parabolē", literally a "placing beside" or "comparison", from "para" (beside) and "ballein" (to throw). The Greek mathematician Apollonius of Perga used the term for the curve, so the word carries the idea of a figure set alongside a line or point rather than any original notion of throwing, even though a thrown object does trace a parabola. The second part, "-oid", comes from Ancient Greek "eidos", meaning "form" or "shape", and it turns a noun into a word meaning "resembling" that noun. Words like "asteroid" (star-like) and "android" (man-like) use the same ending. A paraboloid is therefore something shaped like a parabola, which is why the term describes a surface rather than a curve: it is the three-dimensional figure formed when a parabola turns around its axis.