ORTHOGONAL

Of two objects, at right angles; perpendicular to each other.

Example: "A chord and the radius that bisects it are orthogonal."

Of a pair of vectors: having a zero inner product; perpendicular.

Example: "The normal vector and tangent vector at a given point are orthogonal."

Of a square matrix: such that its transpose is equal to its inverse.

Of a linear transformation: preserving its angles.

Of grid graphs, board games and polyominoes: vertical or horizontal but not diagonal.

Of a pair of elements in an ortholattice: each less than or equal to the orthocomplement of the other.

Statistically independent, with reference to variates.

Of two or more aspects of a problem, able to be treated separately.

Example: "The content of the message should be orthogonal to the means of its delivery."

Of two or more problems or subjects, independent of or irrelevant to each other.