What defines a supplement in the context of publication?

In the context of publication, a supplement refers to a separate publication that is distinct from the regular issue of a journal. This can often include additional research findings, complementary studies, or other relevant content that may not fit within the standard format or scope of a typical journal article. Supplements are usually published alongside the main journal issue, but they are treated as separate entities to highlight specific themes or topics, providing extra content that enriches the main journal's offerings.

This method of presenting information allows for more focused discussion on emerging topics or new data that can be shared with the scientific community without being constrained by the primary journal's standard publishing schedule or formatting requirements. While supplements may include peer-reviewed content, this aspect is not a defining characteristic of what makes something a supplement, which is ultimately about its status as a separate publication.