Depending on context, a supplement can refer to:

• a nutritional supplement taken by people to enhance their diets; it can include vitamins, minerals, fiber, and/or protein, among other additives;
  • bodybuilding supplements, a specific subset of nutritional supplements taken by those wishing to gain muscle mass
• the pet or livestock equivalent of the nutritional supplement, added to Pet foods or fodder, which in addition to the types of additives found in the human equivalent can also include antibiotics or other drugs to improve their resistance to common ailments;
• premixes can be used in supplements; or
• in geometry, a supplementary angle.

Published supplements take various forms, such as:

• a follow-on publication that complements its predecessor, either by bringing it up-to-date (e.g. the Index Catalogue), or by otherwise enhancing the predecessor's coverage of a particular topic or subject matter, as in the Tosefta;
• a newspaper supplement, an often-weekly section of a newspaper, usually in the format of a tabloid or magazine, covering wide-ranging and less time-critical subjects, as in The American Weekly, the 2004 version of Life, and Parade; newspaper supplements became common in France and Germany in the mid to late 19th century--they were called feuillton in French. In Chinese, they are called fukan.
• an advertising supplement which periodically accompanies a newspaper and is prepared by the paper's advertising staff instead of its editorial staff, covering topics such as real estate and automobiles on behalf of the paper's frequent advertisers; or
• a spin-off from a newspaper now sold separately and typically covering a specific topic, such as the Times Literary Supplement and the Times Educational Supplement.