supplements

1. Something added, especially to make up for a deficiency.
2. An extension to a document or publication that adds information, corrects errors or brings up to date.
3. An additional section of a newspaper devoted to a specific subject.
4. An angle that, when added to a given angle, makes 180°; a supplementary angle.
5. (nutrition) A vitamin, herbal extract or chemical compound ingested to meet dietary deficiencies or enhance muscular development.
6. An additional charge, especially for food in a restaurant.

   There is a £2 supplement if you choose the steak.

verb

To provide or make a supplement to something.