Subject headings allow you to search specifically for a subject. Subject headings are also called keywords. but please note: in SmartCat by keyword is also meant any word from the title, the abstract, or the table of contents. In most bibliographic databases a subject heading is an indexed term with which you can make your search more specific. Using such a term you will also find publications where the term does not appear in the title.

Use subject headings to:

• focus your search on a subject.
  In this way you can search for publications in which your subject is not part of the title. For example, if you search using the keywords “gas extraction” and ‘Groningen’, the results will include publications with titles such as ‘Gravity changes and natural gas extraction in Groningen’ and ‘Social impacts of earthquakes caused by gas extraction in the province of Groningen, the Netherlands’, publications that you would not have found if you searched using title words.
   
• find literature in more than one language in a single search.
  This means you do not have to search for Dutch and English literature separately.

Synonyms

Use as many different keywords as possible that mean the same thing (e.g. environmental pollution, environmental contamination).

A thesaurus is the best place to find synonyms.

You can do separate searches for the terms you find, or you can combine them using OR.

You can use the search operators AND, OR and NOT to combine search terms. These are the most commonly known and used operators.

The operators AND and NOT limit the number of results from a search. The operator OR does the opposite; it increases the number of results.

Examples:

• Endangered AND birds : combines these two words
• Endangered OR birds : searches for the words endangered OR birds. This search will produce more results. (Tip: the operator “OR” can also be used to include different spellings and translations or synonyms in the search).
• Endangered NOT birds : searches for the word ‘endangered’ and excludes the word ‘birds’.

To see how this works, take a look at The Boolean machine. Move your cursor over the operators AND, OR and NOT to see how they determine your search.

You can also combine more than two search terms. Use brackets to indicate the priority. For example (Money OR inflation) AND banking.

Truncation (or wildcard symbols) can be used to broaden your search and include different spellings.

To do this, you shorten the search term to a word stem and, depending on which database you are using, you type either a question mark or asterisk after the word stem. The results will then include various endings and spellings.

If you search with environ*, the results will include publications with ‘environment’, ‘environmental’ and ‘environmentally’ in the text and/or title.

A question mark replaces a letter in a word; the results include British as well as American spellings.

For example, if you search with organi?ation, the results will include the British English spelling (organisation) as well as the American English spelling (organization).

If you search with labo?r, the results will include ‘labour’ as well as ‘labor’.

A thesaurus is a list of subject-specific subject headings in a database (not every database has one!).

The thesaurus indicates which terms are broader or more general (BT= Broader terms), which terms are narrower or more specific (NT= Narrower terms) and which related terms (RT) can be used to search the database.

For example:

• environmental pollution (= BT)
• soil pollution (= NT)
• environmental technology (= RT)

• use more specific search terms. A thesaurus is the best place to look for these.
• add an extra search term to your search query (AND)
• search in specific search fields (title words, keywords)
• use limiters (e.g. between specific years, or peer-reviewed articles only)
• search for an exact phrase (use double quotation marks)

Make sure that while limiting your search you do not exclude an important aspect of your subject!

• try to broaden your search terms (search with OR, or an overarching search term)
• try to make your search less precise (e.g. search using “all words”)
• use synonyms
• translate the search terms
• use truncation/wildcards
• use suggested keywords

You can search for a specific expression or concept (e.g. “social media”) by putting the words in double quotation marks. This forces the database to treat the two words as a phrase in the defined order.