Ellipsoid

Part of speech: noun

Pronunciation: /ɪˈlɪp.sɔɪd/

Definitions

1. A three-dimensional shape that resembles a stretched sphere and is defined by its symmetrical properties in relation to its axes
2. A smooth, rounded geometric form characterized by an elongated profile that has no edges and maintains uniform curvature
3. A geometric figure with a closed, curved surface shaped like a flattened sphere, displaying roundness in all directions around its center axis

Etymology: The word is a plain compound: "ellipse" with the suffix "-oid", meaning "resembling" or "in the form of". The suffix comes from the Greek "eidos", meaning "form" or "shape", which passed through Greek adjectives ending in "-eidēs" and then into Latin as "-oīdēs" before reaching English as "-oid". So an ellipsoid is literally a figure that has the form of an ellipse, extended into three dimensions. Its base, "ellipse", traces back to the Greek "elleipsis", meaning a falling short or omission, which is also the source of the grammatical term "ellipsis". The ancient Greek mathematicians used the name for a curve that fell short of a certain condition, and the sense of "falling short" survives in the word's history rather than in its everyday meaning.

Synonyms: oval, egg-shaped