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.

Definition: 2

Crystallography. referable to a rectangular set of axes.

Definition: 3

relating to, consisting of, or involving right angles; perpendicular

Definition: 4

(maths) (of a pair of vectors) having a defined scalar product equal to zero (of a pair of functions) having a defined product equal to zero