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ENGR 471: Keyword Searching

Pott College and Liberal Arts College Librarian

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Shane White
Rice Library
(812) 461-1052

Choosing Keywords

All of the databases and search engines discussed on this guide will respond best to keyword searches using Boolean operators. Things to keep in mind when choosing keywords:

  1.  Keywords represent the essential concepts of a topic or research question.
    Example - "A mechanism or method of reducing emissions in two-stroke engines" can be cut down to this list of keywords:
    • reduce
    • emissions
    • two-stroke
    • engine
  2.  Be sure to brainstorm relevant synonyms and related (broader or narrower) terms. It's not necessary to include every synonym or related term in your search; but not all authors are going refer to concepts by the same terms, so it's always helpful to have a few keyword options if your searches are coming up empty.
    • reduce, minimize, decrease
    • emissions, carbon monoxide, hydrocarbons
    • two-stroke, two-cycle, internal combustion

Combining Keywords with Boolean Operators

There are three Boolean operators in database searching: AND, OR, and NOT. These operators form relationships between words and establish parameters by which database search engines populate results.


Combining terms with AND directs a search engine to provide you with all results that contain all words connected with AND. So, for example, a search for:

two-stroke AND emissions AND reduction

will only return articles that mention all three keywords.

In general, use AND to connect all of the key concepts in a research question or topic.


Combining terms with OR directs a search engine to provide results that contain at least one of the terms provided. For example, a search for:

two-stroke OR two-cycle OR internal combustion

will return articles that mention one, two, or all of these terms.

In general, use OR to connect synonyms and related terms.


NOT directs a database to exclude any results that mention a certain term. For example, a search for:

two-stroke NOT four-stroke

would eliminate any resources that mentioned "four-stroke" engines.