(or thog’ ə nəl) Normal or at right angles.
Linear combinations of functions are orthogonal if they are linearly independent, i.e., if they cannot be expressed as combinations of each other.
The non-vanishing of the determinant of coefficients is a test for the orthogonality of a set of equations.
Orthogonality of vectors xi, xj can be expressed by stating the vanishing of their scalar product, .
Sets of functions may also be considered orthogonal. See Orthogonal functions.