Features of the MeSH Vocabulary


All terms or descriptors listed can be used for online searching. Almost all of them are used for both indexing and cataloging. In the indexing process, indexers assign as many descriptors as are needed to accurately characterize the content of a journal article. Of the 10 to 12 assigned, those representing the most significant points are identified with an asterisk in the online citation. It is under those descriptors that the citation can be located in Index Medicus. The remaining descriptors are used to identify concepts which have also been discussed in the item, but that are not the primary topics.

MeSH has special types of descriptors that are not used in Index Medicus (and thus are never preceded by an asterisk in the bibliographic citation), but that are available for both indexing and online searching. These are:

  1. Publication Types. These descriptors characterize what a publication item is rather than what it is about. The background and philosophy of these types are discussed below. The complete list of Publication Types is provided in a separate section.

  2. Check Tags. These descriptors must be entered for every article citation to which they apply. They are listed on the following page.

  3. Geographics. These descriptors include continents, regions, countries, states, and other geographic subdivisions. They are listed as a group in category Z of the MeSH Tree Structures, the hierarchical classification of MeSH descriptors.

Main Headings

Main headings, the preferred descriptors for vocabulary concepts, appear in large type in both the Annotated and Index Medicus MeSH. Most appear as subject headings in Index Medicus.

Entry Vocabulary

Additional terms are added to create the entry vocabulary. Entry terms provide greater ease of use and accessibility to MeSH. They are synonyms, near-synonyms, abbreviations, alternate spellings, and other alternate forms that may be more familiar or easier to type. Generally, entry vocabulary may be used interchangeably with preferred descriptors for searching of PubMed.

In the Annotated Alphabetic MeSH, printed entry terms are see cross-references to a MeSH descriptor and are also displayed as backward cross-references under the preferred descriptor (see the illustration at NEOPLASMS.

In addition, there are entry terms that are not printed. They consist of variations in the form, word order, or spelling of a descriptor or printed entry term. Trade names of drugs and equipment are usually not printed, but may exist as non-print entry terms.

Publication Types

Publication Types were instituted in 1991 to expand on the concept of the former Citation Types. They provide an additional means for classifying material indexed or cataloged in a variety of NLM databases. Rather than representing the subject content of an article or book, they characterize the nature of the information or the manner in which it is conveyed, e.g., letter, historical article, retracted publication, clinical conference, etc.

All Publication Types are printed in the body of the Annotated MeSH. A list of Publication Types and associated usage is printed in this introduction.The complete list of 2003 Publication Types with scope notes is provided.

Check Tags

These are special use descriptors that reflect parameters or aspects of subject content. Special efforts in indexing assures that these will be included or "checked" each time they appear as aspects of an item being indexed.

The following list of descriptors must be entered by an indexer for every journal article citation to which they apply:

ANIMAL IN VITRO
CASE REPORT MALE
COMPARATIVE STUDY PREGNANCY
ENGLISH ABSTRACT SUPPORT, NON-U.S. GOV'T
FEMALE SUPPORT, U.S. GOV'T, NON-P.H.S.
HUMAN SUPPORT, U.S. GOV'T, P.H.S.

Subheadings (Qualifiers)

Subheadings (or qualifiers) are used in indexing, cataloging, and online searching to qualify MeSH descriptors by pinpointing some specific aspect of the concept represented by the descriptor. For example, "LIVER/drug effects" indicates that the article or book is not about the liver in general, but about the effect of drugs on the liver.

In the past, there were four types of subheadings. Only topical subheadings are in current use. Form, language, and geographic subheadings, previously used in cataloging, are no longer used by NLM catalogers but are found in NLM's distributed cataloging records as described in the Cataloging Practices section. Topical subheadings appear alphabetically along with descriptors and cross-references in the Annotated MeSH; they are printed in lower case preceded by a slash, e.g., /etiology.

The section entitled Topical Subheadings with Scope Notes, Abbreviations and Allowable Categories is a complete listing of topical subheadings with definitions, years of entry, abbreviations, and use by tree categories.

Tree Numbers and Position

Tree numbers show the position of a descriptor relative to others within a subject area. For example, specific cranial nerves are assigned Tree Numbers that show they are subordinate to Cranial Nerves, the broader descriptor. MeSH subject descriptors have at least one tree number that gives the location of the descriptor in the hierarchical classification printed as MeSH Tree Structures. This structures helps you to search for the most general or broad aspects of a topic, select more specific areas, or include all aspects within a narrow area. Since descriptors may appear in more than one tree, the Tree Number may be used to identify the specific location of most interest within the context of related topics.

Indicators of Related Concepts

Three kinds of informative references may be found in descriptor records: see related, consider also, and main heading/subheading combination references (see the NEOPLASMS illustration). These suggest other descriptors in MeSH that relate to the subject and that may be useful in indexing, cataloging, or searching a particular topic.

See related references indicate the presence of other descriptors that relate to the topic conceptually, e.g., NAVAL MEDICINE see related DIVING. Some relationships are recognized routinely: between an organ and a procedure (e.g., BILE DUCTS see related CHOLANGIOGRAPHY); between an organ and a physiological process (BONE AND BONES see related OSTEOGENESIS); between a physiological process and a related disease (BLOOD PRESSURE see related HYPERTENSION). Drugs and chemicals also show standard relationships through the see related device as well. These relationships include those between an organ and a drug acting on it (BRONCHI see related BRONCHOCONSTRICTOR AGENTS); or between a physiological process and a drug acting on it (BLOOD COAGULATION see related ANTICOAGULANTS), etc.

The consider also notation is primarily used on anatomical descriptors. It indicates the presence of other descriptors that relate to the topic linguistically, e.g., BRAIN consider also terms at CEREBR- and ENCEPHAL-. Note that the consider also refers to groups of descriptors beginning with a common stem rather than to a single descriptor.

The main heading/subheading combination notations refer an invalid (and prevented) main heading/subheading combination to the preferred precoordinated descriptor expressing the equivalent concept. For example, at the entries for the descriptors ACCIDENTS, AORTA, and ARM, the references read:

ACCIDENTS/prevention & control see ACCIDENT PREVENTION
AORTA/radiography see AORTOGRAPHY
ARM/injuries see ARM INJURIES

Annotations and Other Narrative Information

Three kinds of notes may follow a MeSH Descriptor or Topical or Form Subheading in the body of this publication:

  1. Indexing and Cataloging Annotations are written for indexers and catalogers. Online searchers will certainly benefit from these additional insights into the practices prescribed for those who create the databases. Further information about annotations may be found in the sections entitled Indexing Annotations and Cataloging Practices, respectively.

  2. History Notes are written for online searchers and catalogers. They consist of dates of entry of MeSH descriptors and trace changes in form, status, and mapping of descriptors, as well as changes in status and referred-to descriptors of entry terms. Further information about history notes may be found in the History and Online Notes section.

  3. Online Notes were written for online searchers, predominantly for assistance in retrospective searching. Many of these notes reflect descriptor changes for citations stored in the computer under a different descriptor from that under which they were published in Index Medicus previously. These notes reflect ELHILL syntax and should be modified in line with the specific search system being used. Further information about Online Notes may be found in the History and Online Notes section.

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Last updated: 18 October 2002