oidal

Oidal is an adjective describing something that resembles an ovoid, or egg-shaped, object. It is used primarily in technical writing to indicate approximate three-dimensional form rather than exact geometry, and it can apply to objects whose cross-sections are oval or whose overall silhouette is egg-like.

Etymology and relation to other terms: Oidal originates from the broader suffix -oid, meaning “like” or “resembling,” with the adjectival -oidal form used to describe shape. The base word ovoid denotes the egg-shaped form itself; oidal emphasizes resemblance or likeness rather than a strict geometric definition. In practice, ovoidal or ovoid-shaped are often used interchangeably with oidal.

Usage: In biology, oidal may describe cellular shapes, pollen grains, or other structures that are roughly egg-shaped. In geology or paleontology, the term can describe grains or fossils with an ovoid contour. In geometry or computer graphics, oidal describes a shape that is close to but not identical with an ellipsoid or sphere, conveying a softer or more irregular egg-like form than precise terms might imply.

See also: ovoid, ovoidal, ellipsoid, toroid.