Main entry: accessory, add-on, appurtenance, supplement
Definition: a supplementary component that improves capability
Main entry: supplement, supplementation
Definition: a quantity added (e.g. to make up for a deficiency)
Main entry: addendum, postscript, supplement
Definition: textual matter that is added onto a publication; usually at the end
Main entry: supplement, append, affix, add on
Definition: add to the very end
Usage: He appended a glossary to his novel where he used an invented language
Main entry: supplement
Definition: add as a supplement to what seems insufficient
Usage: supplement your diet
Main entry: supplement
Definition: serve as a supplement to
Usage: Vitamins supplemented his meager diet