Definitions of supplement:

• noun:   a quantity added (e.g. to make up for a deficiency)
• noun:   textual matter that is added onto a publication; usually at the end
• noun:   a supplementary component that improves capability
• verb:   add as a supplement to what seems insufficient

  Example: "Supplement your diet"

• verb:   serve as a supplement to

  Example: "Vitamins supplemented his meager diet"

• verb:   add to the very end