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Medline Guided Exercise: 3. Keyword Search

3.  Add a Keyword Search

What is a Keyword?

Keywords are specific words which are found in the title and abstract.  Keywords are also called textwords or natural language. 

In this module, you will learn how to find relevant keywords, or natural language for our first, or P, element.

Remember, for each PICO element we will perform both a Subject Heading and a Keyword search.  Each type of search has different advantages that will make our search more relevant.

Keywords are helpful when:

  • An appropriate MeSH does not exist
  • The term is very specific, jargon or a brand name etc.
  • The concept is new to the literature
  • The search Term is a condition or therapy that is very rare
  • The paper has not been indexed as it is either too recent, or not indexed in Pubmed

Be aware: In most databases the search engine is looking for a match of the keyword in the Title and Abstract, not the full text.

When using keywords or natural language we need to take into account:

  • Spelling variations
  • Synonyms
  • Plural forms 

Many of these can be addressed by using Wildcards.  See: Using Wildcards below.

Now let's do the keyword search. 

Consider again the research question: "What research has been done on the use of games such as Wii, Kinnect and others for improving balance in children and teenagers who have a traumatic brain injury including concussion."

In Step 2, we identified the subject headings Brain Concussion as well as Brain Injuries, Traumatic.

For each concept search we will perform a related keyword search in addition to the Subject Heading Search.

From the Used For list in the Scope Note for brain concussion and traumatic brain injury we noticed that related keywords for our subject headings are: Concussion and Brain Injury as well as their plural forms.

Step by Step: Adding a Keyword Search

Keyword Search

  1. Under the OVID search bar, uncheck the checkbox “Map Term to Subject Heading”
    • Type our first keyword: concussion*
      • The asterisk * is a method of truncation - see Using Wildcards
    • Type the operator word: OR
      • See Using Operators for more information on operators
    • Type our second keywords as: brain injur*
    • Your search query should now look like: concussion* OR brain injur*
    • Click Search
  2. Your search is displayed under your previous search in your Search History(Figure 1) with .mp on the end. This indicates that it is a keyword search.
Video Demo: Keyword Search


Venn Diagram: Boolean Operator OR
Boolean Operator OR

Venn Diagram: Boolean Operator AND
Boolean Operator AND
Operators are syntax to combine search terms
  1. OR : Retrieves any or all search terms; therefore retrieves mORe results
  2. AND : only returns results that contain ALL search terms; therefore returns few results

Wildcards / Truncation

  • Wildcards are useful for finding variations in the spelling of the search term.
  • Truncation is used to find variations in the ending of search terms
    • Asterisk (*) wildcard at the end of a stem will capture variations to the end of the term of any length
    • injur* will return both "injury", "injuries"
    • arm* will return arms, armies, armadillo etc. [see tip under ?]
  • Wildcards # and ? are useful for finding variations in spelling and can be used in various situations. For example:
    • # stands in for precisely 1 character e.g.Wom#n finds 'woman' or 'women'; randomi#ed find 'randomized' or 'randomised'.
    • ? stands in for 0 or 1 character and can be used in various situations
      • For British and American spelling e.g. colo?r finds colour or color.
      • For endings e.g arm? finds arm or arms
  • For more details see the Truncation and Wildcard Symbols Guide

Proximity Operator

The adjacency, or proximity, operator is used to increase the relevancy and specificity of the keyword search

  • ADJ together with any number (ADJ#) specifies how close two words can be to each other by specifying the number of words between each
  • For example:
    • ADJ3 finds 2 search words with 3 or less words between them and in either direction
    • The search: "hip adj3 replacement" will find results including "replacement of the hip" as well as "hip replacement".
    • The search: "Wait adj5 list" will find results including "wait time on the booking list" as well as "wait list".
  • For more details see the Truncation and Wildcard Symbols Guide

Continue building your search

  1. Using steps 1-2 for the keyword search, find suitable keywords for your P, or first, concept.
  2. Type your keyword in the search box
  3. Click Search to add it to your search history
  4. Note: If Medline displays a list of subject headings, disregard and scroll down to the end of the list to find your search term. It will be in black and have .mp]


  • Think of all types of words that match your concept
  • Are there any synonyms?
  • Are there variant spelling and endings? Can I use truncation?
  • Is there a suitable wildcard to incorporate any variations?
  • Words next to each other are searched as a phrase - no need to use quotes