Rectilinear

Rectilinear is an adjective used in geometry and related fields to describe objects, motions, or coordinate systems that are defined by straight lines. The term derives from Latin rectus, straight, and linea, line.

In geometry, a rectilinear figure is composed entirely of straight-line segments; a rectilinear polygon has edges that are straight and interior angles that are typically multiples of 90 degrees in the common form. The term is commonly used to distinguish straight-edged shapes from curved ones.

Rectilinear motion refers to motion along a straight line, often described in one dimension. In physics and kinematics, it describes straight-line motion with constant or variable speed along a straight path.

In photography and optics, a rectilinear lens projects an image so that straight lines in the scene appear straight in the photograph, in contrast to curved distortion produced by some wide-angle or fisheye lenses.

In cartography and computer graphics, rectilinear grids and projections maintain straight grid lines; a common example is the rectilinear (plate carrée) projection where latitude and longitude are represented as straight lines. This approach can simplify calculations and rendering but may introduce distortion away from the standard orientation.

See also Cartesian coordinates, orthogonality, and distance metrics such as the rectilinear (L1) distance.