Publication Types (Publication Characteristics) are Descriptors that indicate what an indexed item is, (i.e., its genre, rather than what it is about - for example, Historical Article). They may include Publication Components, such as Charts; Publication Formats, such as Editorial; and Study Characteristics, such as Clinical Trial.
They function as metadata, rather than being about the content. These records are searchable in PubMed as Publication Type [PT], and the terms in MEDLINE records are labeled as "PT" or rather than "MH" or . They are listed in category V of the MeSH Tree Structures.