Keywords search free text words and phrases.  When using Library Search or subject databases (some database are keyword databases), your keywords are normally matched against words in the author, title and abstract fields. Authors can use their natural language to describe their work (they may use different subject jargon or a variant spelling to your keywords), it can feel like a bit of a guessing game knowing which keywords to try. In reality your search will only retrieve results that match the keywords that you type in. It is vital to think about alternative terminology that authors may have used in order not to miss out on any research. 

You have already started to identify some keywords and alternate words in your scoping search, here are some top tips for finding more:

• Talk to friends/supervisors... just talking about your topic with someone else can generate additional words.
• Read! The more you read on your subject, the more keywords and synonyms you will discover. Remember to have a notepad when you are reading, to note down these additional words. 
• Use an online thesaurus, e.g. http://www.thesaurus.com/, or just type the keyword in Google with the word 'synonym' after it (e.g. 'effect synonym') and Google will suggest various online thesauri to use.
• Use a database with a subject thesaurus to check alternative words.  Look through your subject guide in the 'Journals and Databases' page.
• When you retrieve a relevant record remember to check out the subject headings or index terms (how the article has been indexed or catalogued which you will often find when you click on  the record) that have been used in this specific article .  This is a very effective way of finding alternative words to include in your search. 

Identifying other relevant systematic reviews:

A published systematic review should include at least one example of the search strategy used. This is a good way of identifying the search string, subject headings and keywords.  If you found any relevant published systematic reviews you could look at the search strategies used in these reviews to identify further subject headings or keywords.

What is controlled vocabulary? 

A controlled vocabulary is a standardised, pre-defined set of terms used by some databases to describe and categorise articles or information based on their content. It is used to ensure that searches retrieve all relevant results, even when the authors use different terms to those which you are using. This can be very helpful, and save a lot of time, as you are not having to guess which keywords an author may have used. 

How do you use controlled vocabulary? 

Controlled vocabulary may also be referred to as subjects, subject headings, subject terms, descriptors, thesaurus, or index terms, depending on which database you are using. 

However, controlled vocabulary is at its most effective when you combine it with your own keywords. Using keywords alongside a controlled vocabulary means that you can pick up misspellings, plus any articles that an indexer may have missed (they are only human after all) and articles waiting to be indexed.

Different databases use different controlled vocabulary datasets, and they usually suggest the appropriate terms to you when you enter your search term. This is why it is important to search each database individually, rather than searching several databases across a supplier's platform. For example, if you search across the entire EBSCO platform, rather than individually searching EBSCO's databases (such as the British Education Index or Business Source Complete), then you won't find the most relevant information, as you won't be able to apply two different controlled vocabulary datasets to one search. 

Databases and platforms that use controlled vocabulary include:

ASSIA, Social Sciences Database, Sociology Database, Sociological Abstracts, ERIC - Proquest Thesaurus

British Education Index (EBSCO) - Thesaurus of education terms

CAB Abstracts - CAB Subject Thesaurus

Child Development & Adolescent Studies (EBSCO) - Thesaurus of Education Terms 

CINAHL - CINAHL headings 

Compendex (Engineering Village) - Ei Thesaurus

Educational Abstracts (EBSCO) - Thesaurus of Education Abstracts (H. W. Wilson)

Educational Administration Abstracts (EBSCO) - Thesaurus of Education Terms 

Embase - EMTREE (Embase Subject Headings)

ERIC (EBSCO) - ERIC descriptors

GreenFILE - (EBSCO) Green Thesaurus

Medline, The Cochrane Library - MeSH (Medical Subject Headings)

PsycInfo - APA Thesaurus

To find out more about the different databases and how to search them (including how to use the controlled vocabulary in them) see the Database Help below.