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Biology: Essential Search Techniques

Essential Search Techniques: Boolean Operators, Truncation, and Phrases

Almost all bibliographic databases, as well as Quick Find our library catalogue, allow you to use Boolean operators, truncation, and phrases in your search statements. Using these can make your searches more effective.

Boolean Operators

The Boolean operators (named after 19th-century logician George Boole) are AND, OR, and NOT.

         cat AND dog    This retrieves items that have the word cat and the word dog.
  cat OR dog This retrieves items that have the word cat or the word dog.
  cat NOT dog This retrieves items that have the word cat but not the word dog. Use this with caution.


Boolean operators can be grouped with parentheses:

(cat OR feline) AND (dog OR canine)

Note: Most search engines do not require that Boolean operators be written in capital letters. However, a few do. If in doubt, capitalize.


Truncation is used to retrieve items having various forms of words. It is especially useful for finding singular and plural forms of nouns.

In most database search engines, and in Quick Find, the truncation symbol is the asterisk ( * ).

hormon*    This retrieves items that have hormone, hormones, hormonal, hormonic, hormonology, etc.


Phrases are sequences of words that appear together in the order specified. Use double quotation marks to indicate phrases.

"global warming"   This retrieves items having this phrase, but not items in which global appears somewhere and warming appears somewhere else, but not next to each other in that order.