[from mathematics] Mutually independent; well separated; sometimes,
irrelevant to. Used in a generalization of its mathematical meaning to
describe sets of primitives or capabilities that, like a vector basis in
geometry, span the entire ‘capability space’ of the system and
are in some sense non-overlapping or mutually independent. For example, in
architectures such as the *PDP-11** or
VAX where all or nearly all registers can be used
interchangeably in any role with respect to any instruction, the register
set is said to be orthogonal. Or, in logic, the set of operators not and or is orthogonal, but the set nand, or,
and not is not (because any one of
these can be expressed in terms of the others). Also used in comments on
human discourse: “This may be orthogonal to the discussion,
but....”*