Orthographic projection is a means of representing three-dimensional objects in two dimensions. It is a form of parallel projection, in which all the projection lines are orthogonal to the projection plane, resulting in every plane of the scene appearing in affine transformation on the viewing surface. The obverse of an orthographic projection is an oblique projection, which is a parallel projection in which the projection lines are not orthogonal to the projection plane.
The term orthographic is sometimes reserved specifically for depictions of objects where the principal axes or planes of the object are also parallel with the projection plane. However, these are better known as primary views in multiview projection. Furthermore, when the principal planes or axes of an object in an orthographic projection are not parallel with the projection plane, the depictions are sometimes referred to as axonometric. However, these are better known as auxiliary views. (Axonometric projection might be more accurately described as being synonymous with parallel projection.) Sub-types of primary views include plans, elevations, and sections. Sub-types of auxiliary views might include isometric, dimetric, and trimetric projections.
A lens providing an orthographic projection is known as an object-space telecentric lens.