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ENGL 199H / HSERV 100: Library databases & techniques for literature reviews

Developing search terms

Developing search terms from your research question

First consider:

  1. What is your research question?
  2. What are the key concepts of your question?

Example: What is the effect of traffic-related air pollution on blood pressure?

Gather synonyms for each part of the question. Finding a few good articles by searching your key words in the article title. Looking at the subject words, indexing terms, or author keywords for a relevant article can help identify synonyms and related concepts.

List the terms and synonyms for each concept in a separate line.

  1. vehicle*, traffic, trucks, cars
  2. exhaust, pollution, emissions, fumes
  3. blood pressure, hypertension


Enter your search terms in separate lines in the database search engine

1: vehicle* OR traffic OR trucks OR cars

2: exhaust OR emissions OR pollution OR fumes

3:  blood pressure OR hypertension

Combine the three concepts to find citations that have at least one term from each grouping.

4. 1 AND 2 AND 3

Notes about Connectors (OR, AND, NOT)


Use “OR” when searching synonyms or alternative terms. Articles containing any of the ORed words will appear in the search results. 

(wine OR chocolate) AND heart health


Terms connected with “AND” must all show up in each article retrieved.


“NOT” will remove articles containing particular terms. 

(smoking AND cancer) NOT children – eliminates articles discussing children, including articles that discuss both adults and children.


You can combine terms into one search statement successfully by placing the terms in parentheses that you want to process first:

Blood pressure AND (vehicle* OR traffic) AND (emissions OR particulates OR exhaust)


Too many or too few citations

No References or Too Few References

  • Look for misspellings in your strategy.
  • Decrease the number of concepts searched.
  • Try a broader search term.
  • Use terms from a good, known, article citation's descriptors or subject headings for searching.
  • Increase the number of synonyms or alternatives for a term.
  • Use a truncation symbol at the end of a term to pick up variant endings.  The asterisk (*) is the truncation symbol used in some databases.  Example:  asthm* will retrieve asthma or asthmatic.
  • Try a different database.

Too Many References

  • Choose the most significant key words.
  • Add additional concepts to your search to narrow focus.
  • Limit your search by language, current years, etc. by using Filters.
  • Ask for significant words to be in the TITLE of the article.