2. That which fills up, completes, or makes an addition to,
something already organized, arranged, or set apart;
specifically, a part added to, or issued as a continuation
of, a book or paper, to make good its deficiencies or
correct its errors.
3. (Trig.) The number of degrees which, if added to a
specified arc, make it 180[deg]; the quantity by which an
arc or an angle falls short of 180 degrees, or an arc
falls short of a semicircle.
Usage: {Appendix}, {Supplement}. An appendix is that which is
appended to something, but is not essential to its
completeness; a supplement is that which supplements,
or serves to complete or make perfect, that to which
it is added.
Causes of one kind must be supplemented by bringing to
bear upon them a causation of another kind. --I.
Taylor.