Mathematics .

Also, orthographic. pertaining to or involving right angles or perpendiculars

an orthogonal projection.

(of a system of real functions) defined so that the integral of the product of any two different functions is zero.

(of a system of complex functions) defined so that the integral of the product of a function times the complex conjugate of any other function equals zero.

(of two vectors) having an inner product equal to zero.

(of a linear transformation) defined so that the length of a vector under the transformation equals the length of the original vector.

(of a square matrix) defined so that its product with its transpose results in the identity matrix.

Crystallography . referable to a rectangular set of axes.