Choosing and combining search terms
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Choosing search terms
Search terms are often subject keywords but can also be names, molecular formulae, significant numbers, depending on what you are searching for and the source you are using. This page is focused on choosing subject keywords.
A good way to identify the important search terms for a search:
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Define the subject in one sentence, for example;
- The impact of coastal pollution in Britain
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Split this sentence into concepts, discarding words which merely describe the relationship between one concept and another;
- Coastal Pollution Britain
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For each of the concepts think of synonyms (words with similar meaning) or related terms that would be useful. Some databases, abstracts and indexes have a thesaurus which can help. Look up your terms in the thesaurus and this will tell you related or preferred terms, for example:
- Costal; coast, coasts, beach, beaches
- Pollution; oil, sewage
- Britain; United Kingdom, UK, England, Scotland, Wales, British Isles, Ireland
- Use these terms in your search. The way that you input and combine terms will depend on the source that you are using. Most databases, and the library catalogue, allow you to add truncation or masking symbols to words. For example, entering coast* into a catalogue search will find any word beginning with coast, including coast, coasts and coastal. A printed guide to 'Advanced searching on the Web catalogue' explains more fully, as does help on the system. Some databases use a thesaurus or controlled indexing which will help you to choose the preferred term, and indicate related terms. If you are searching for more than one search term see combining search terms below.
Combining search terms in your searches
When you carry out a Basic Search using the 'Find in all fields' or 'contains' options on the Library Catalogue (https://www.lib.bris.ac.uk/ALEPH/), it automatically links the search terms you have input and displays results which have all the terms present, i.e. term 1 and term 2 and .... However, on the Catalogue and most other databases, you can specify how the search terms are combined. To do this you need to use Boolean logic or logical operators, AND, OR, and NOT or their equivalents on the system you are using. The Advanced search option, accessed via the Advanced Search link on the Basic Search page of the Catalogue, gives these options for you to choose between on the screen. You can also use one or more of these operators to combine a number of terms within a search box in Advanced Search or Basic Search on the Catalogue.
The following examples show how the different operators work.
Advice is also available about how to how to refine your search on the Catalogue.
AND
Use AND if you want to retrieve references that contain both of the terms you are using. This can narrow a search to find fewer, more relevant, references.
eg Pollution AND Oil spills
OR
Use OR if you want to retrieve references that contain either one of the terms you are using, or both terms together.
This can broaden a search to find more references.
eg Pollution OR Oil spills
NOT
Use NOT if you want to exclude references that contain a particular term. Use with caution!
eg Pollution NOT Oil spills
Brackets
Also, many databases allow you to use brackets to make more complicated searches, for example:
(Pollution OR Oil) AND Seabirds.
The brackets indicate the order that the combining of terms is made in.
Alternatives to AND, OR, and NOT
Some databases and search engines may use other symbols in the place of AND, OR, and NOT.
For instance, with Google:
- 'Pollution Seabirds' is equivalent to Pollution AND Seabirds (the AND is implied)
- +oil means that oil must be present
- OR is used as above
- -music is the equivalent of NOT music
To get the best out of search tools we recommend you look at the help on the system to find out how to enter and combine search terms effectively.