[n] a supplementary component
[n] a quantity added (e.g. to make up for a deficiency)
[n] textual matter that is added onto a publication; usually at the end
[v] add to the very end; "He appended a glossary to his novel where he used an invented language"
[v] add as a supplement to what seems insufficient; "supplement your diet"
[v] serve as a supplement to; "Vitamins supplemented his meager diet"
add, annex, appendix, attach, auto accessory, back matter, be, component, comprise, computer accessory, constituent, constitute, continuation, cut-in, eke out, element, end matter, fill out, fitting, fixings, furnish, increase, increment, insert, leverage, make up, matter, provide, render, represent, sequel, supply, trimmings, vitaminise, vitaminize