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BIO 115

Search Tips and Tricks

There are four basic techniques you can use to improve your search skills: Boolean expressions, keyword searching, subject searching, phrase searching, and truncation. All of these techniques can be combined together to create precise or broad searches.


Boolean searching is a way to tell the computer to do certain things with keywords that you are using in your search. If you want more help try out the tutorials linked below.

AND (find all)

When you combine keywords with AND you will only get results which contain all of the keywords joined by AND.
Use AND when you need to narrow a search to contain ALL keywords.

Example search: cat AND dog
Search results will only contain items which contain the words "cat" and "dog"; search results will exclude items only on cats or only on dogs.

OR (find either)

When you combine terms with OR you will get results which contain any of the terms joined by OR.
Use when you want to broaden a search to search for related terms or variant spellings (example: "climate OR climatic OR climates")

Example searchcat OR dog
Search results will contain items which contain only "cat", only "dog", and items which contain both both "cat" and "dog."

NOT (ignore)

NOT is used to specify keywords to ignore. Some search engines and databases don't support NOT (Google uses "-" instead for example). NOT can be useful when you are searching for a word with multiple meanings or need to exclude certain topics from a search.

Example searchgang violence NOT motorcycle
These search results should only cover non-motorcycle related gang violence.


Most of us are familiar with keyword searches: you enter in words and you get back results which contain those words. It's important to choose your keywords carefully otherwise you will get no results or the wrong results. Use these basic tips to improve your keywords:

  • Choose the most basic form of a word to use in a search (i.e. use "pizza" instead of "pizzeria")

  • Avoid contractions, uppercase letters, and punctuation.

  • Do not search in sentences or sentence fragments (unless it's a phrase).


Subject Headings  are:


  • “controlled” vocabulary used by an organization (e.g. the National Library of Medicine) to describe the concepts in the literature collected by that organization or database (such as MEDLINE or CINAHL).
  • Consistent in their definition across the records in the database.
  • Less flexible and must be chosen from the thesaurus used by the database; if the incorrect subject heading is selected, none of the results will be relevant.
  • Only searched for in the subject heading field of the record.
  • Helpful for retrieving a set of articles with fewer irrelevant results
  • Slow to change--this means that the most recent changes in knowledge--on diseases, drugs, devices, procedures, concepts--may not be reflected in the controlled vocabulary.


The chart below shows some examples of keywords and the equivalent subject headings in CINAHL and MEDLINE

Graph of differences between keywords and subject headings. Examples include the keyword "heart attack" versus the subject heading "myocardial infarction"

Note that the Subject Headings in CINAHL and MEDLINE are not always the same. In the last example--LGBT--note that while CINAHL has a subject heading for the term, MEDLINE requires that two different subject headings have to be combined to create an equivalent. For more information on how to combine related MeSH terms, see the next page.

Some basic guidelines are:

  • If the term or topic is very recent, keywords may be the best option
  • If no Subject Heading exists for your term, or seems inadequate, use a keyword
  • If the keyword is too vague or broad, a Subject Heading may help focus your search and eliminate too many results
    • e.g. neuroses would be a very broad keyword search
  • If you want a very comprehensive literature search, you should use both a keyword and a subject heading
    • e.g. Heart attack OR Myocardial Infarction


Phrase searching

To search for a phrase or multi-word concept place the words or phrase in quotation marks. The quotation marks tell the search to find all of these words together in this order.

Example searches:
"To be or not to be" AND shakespeare
"new york city"
"unmanned aerial vehicle"


Truncation is a way to place "wildcard" characters in your searches. This is useful when trying to include word variations in your searches.You need to be careful where you truncate a word - if you truncate too early you may end up with unexpected results that contain unrelated words with the same spellings. The asterisk(*) is the symbol most indexes use for truncation.

Example good truncation search: bacteri*
This search will return results for bacteria and bacterium. This is a good use of truncation.


Example bad truncation search: creat*
This search will return results for: creaturecreationcreatecreatingcreator, etc. This is not a good use of truncation.

Combining Techniques

You can combine multiple search techniques and if you have a complex search you can use parentheses to group different sets of instructions:

Example searches: (cat or cats) AND "house train*"

This search will retrieve results that contain the phrases "house training" or "house train" and EITHER cat or cats. If you truncate cat* you would get way too many irrelevant results including catatonic, catalyst, etc. so only train is truncated.