noun
ellipsoid
A mathematical term for a three-dimensional surface whose plane sections are ellipses or circles. Used in geometry and related fields.
地球は完全な球ではなく、楕円面に近い形をしている。
The Earth is not a perfect sphere; it has a shape close to an ellipsoid.
球面 is a spherical surface, a special case of an ellipsoid where all axes are equal.
Compound of 楕円 (ellipse) and 面 (surface). The term directly describes the geometric concept.