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This guide © 2025 by UCL - Library Skills is licensed under CC BY-NC-SA 4.0 
A subject heading is like a tag, or a label, which describes what the item (book, article, etc.) is about.
Subject headings are useful because they provide a consistent way of describing the subject matter of the item. When an item is added to a database, an indexer or automated programme will decide which topics are covered by the article, and choose several subject headings to apply.
The subject headings are selected from a standardised list, or thesaurus; this is known as a ‘controlled vocabulary’. This means that all items about a particular subject are tagged with the same, standard subject heading, regardless of the words and phrases the author used in the title or abstract.
E.g. Let’s say you’re looking for articles about nosebleeds, so you search for nosebleed* in the title or abstract.
There are 519 articles with the word nosebleed or nosebleeds in the title or abstract.
However if you search for the correct subject heading for nosebleed, which is epistaxis, you obtain far more results. (Note that in the screenshot MeSH stands for Medical Subject Headings)
The principle does not only apply to medical terminology.
E.g. If you wanted to find articles about people who are trying to stop smoking, you could do a textword search for terms such as ‘reduction in smoking’ or ‘quit* cigarettes’, but you could also use a suitable subject heading such as Smoking Cessation, Smoking Reduction, or Tobacco Use Cessation.
Searching by subject heading means you have a better chance of finding all items about that subject, even if the authors used words or phrases you didn’t think of.
Subject headings are also useful for finding records where there is no abstract, items in foreign languages, or items which have non-descriptive titles.
Find appropriate subject headings by searching in the subject heading field, or browsing the thesaurus, for the database you are using. Not all databases use subject headings, but those that do will each have their own unique thesaurus.
Take a look at the explanation (sometimes called the ‘scope note’) for the heading if available, to make sure the heading reflects the subject you are looking for.
You can then search the database for all items tagged with that heading, and incorporate your subject heading search into your overall search strategy. Here is an example of how a simple search including subject headings might be constructed.
See our guides to individual databases for more help, or consult the help pages for the database you are using.
Important points to remember:
Remember, not all databases use subject headings, and subject headings do differ between databases. For information on how to use subject headings in specific databases please see the database's help pages. You might also find our guides helpful:
