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.
2.
Crystallography. referable to a rectangular set of axes.
1570s, from French orthogonal, from orthogone, from Late Latin orthogonius, from Greek orthogonios "right-angled," from ortho- "straight" (see ortho-) + gonia "angle," related to gony "knee" (see knee (n.)). Related: Orthogonally.