saddlelike

Saddlelike is an adjective describing a form or contour that resembles a saddle: curved in two directions, typically concave along one axis and convex along the perpendicular axis. In geometry this implies a surface with negative Gaussian curvature, such as a saddle surface. These surfaces bend upward in one direction and downward in the other, producing a shape that is neither a maximum nor a minimum at a given point.

In mathematics, classic examples include the hyperbolic paraboloid and other saddle surfaces used to illustrate curvature properties; their principal curvatures have opposite signs.

In anatomy, saddlelike describes joints with saddle-shaped articular surfaces. The best-known example is the carpometacarpal joint of the thumb, a true saddle joint that permits opposition by allowing movement in two perpendicular axes, though the surfaces are incongruent in other directions. The term is sometimes used to describe other surfaces or articulations with saddle-like topology.

In other disciplines, saddlelike describes landscapes with passes or ridges formed by saddle-shaped topography, helping distinguish such features from domed or trough-like forms.

The word derives from the resemblance to a horseback saddle; its usage is descriptive and varies by field. Related terms include saddle point (in calculus), saddle joint (anatomy), and saddle-shaped surfaces in geometry.