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How to Use the Library

NEW! Learn how to navigate the Gellert Library's resources
The key to being a savvy online searcher is to use common search techniques that you can apply to almost any database, including article databases, online catalogs and even commercial search engines like Google.

Keywords vs. Subjects

Keyword searching is how you typically search web search engines: You think of important words or phrases related to your topic and type them in to get results. This approach will definitely work with the Gellert Library's search tools, especially with well-chosen key words.

To take your searches to the next level, you can use subject headings to find relevant items on the same topic. Databases assign subject headings to describe the content of each item in a database, so searching by subject headings (a.k.a., descriptors) is the most precise way to search article databases.

Keywords Subject Headings
natural language words describe your topic (good to start with!) pre-defined "controlled vocabulary" describes the content of each item (book, journal article) in a database
more flexible for searching because keywords can be combined in many ways less flexible for searching because users need to use the exact subject heading (a.k.a., controlled vocabulary)
database looks for keywords contained anywhere in the record, including title and full-text database looks for subjects only in the subject heading or descriptor field
may yield too many or too few results avoids yielding too many results by using subheadings to focus on one aspect of the broader subject
may yield many irrelevant results usually yields very relevant results

But it's not always easy to guess which subject headings are used in a given database. For example, if you looked up "Movie Theaters" in the old-fashioned Yellow Pages, you wouldn't find any results until you flipped through to the subject heading "Theatres - Movies." So where should you go to figure out which terms to use?

Library of Congress

A good starting point is the Library of Congress, where subject headings got their start. Begin by visiting the Library of Congress's catalog, and then click "Browse."

In the drop-down menu, select "SUBJECTS containing," and try a few different possible subject headings. You'll probably find dozens or hundreds of subject headings. Take note of the ones that seem especially relevant to your actual research interest.

To find narrower, more precise options for your subject headings, try repeating your search with "SUBJECTS beginning with."

You can use these Library of Congress subject headings ("controlled vocabulary" terms) for your searches in NDNU's DISCOVERY, Advanced Search, and database searches.

Subject Headings within Search Interfaces and Databases

You can also find subject headings during your search process.

When searching through DISCOVERY and Advanced Search, which use WorldCat, subject headings will appear in the item description.

Clicking these subject headings will deliver additional results that fall under that subject. This is a great technique to use to find related and overlapping terms.

Check out these tutorials on searching using subject headings in our EBSCO and ProQuest-hosted databases.

Boolean Operators

Boolean operators—the terms AND, OR, and NOT—form the basis of database logic. They connect your search terms together to either narrow or broaden your set of results.

You can use these operators in combination with your search terms and in different search fields to both broaden and narrow your search results. They can be especially helpful in research involving multiple terms, or terms with multiple meanings.

You'll notice that the Advanced Search tool includes Boolean operators built-in:

Using the drop-down menus, you can modify the Boolean operators and search fields.  Each of the Boolean operators has a different effect on a search engine, and these effects can be combined to to help you find all relevant resources (and exclude irrelevant sources).


Use AND to narrow your search results. This operator tells the database that all of your search terms must be present in the resulting records.


Use OR to broaden your search results. This operator tells the database that any of your search terms can be present in the resulting records.


Use NOT to narrow your search results by excluding words from your search. This operator tells the database to ignore concepts that may be implied by your search terms.

Search Order

Because databases follow the commands you type in and return results based exactly on those commands, you'll need to pay close attention to the logical order in which words are connected by Boolean operators.

Databases usually recognize AND as the primary operator, so they connect concepts with AND together first. If you use a combination of AND and OR operators in a search, enclose the words to be "ORed" together in parentheses, similar to an algebra equation.

For example, if you were writing a paper on the ethics of cloning and wanted to compare other kinds of reproduction, you might run searches like these:

  • ethics AND (cloning OR reproductive techniques)
  • (ethic* OR moral*) AND (bioengineering OR cloning)


Truncation easily expands your search and increases your results by gathering sources that mention multiple forms of the same word or word root, saving you from running a separate search for each version of your keyword. 

To use truncation, place an asterisk (*) right where you want to cut the word off, creating what's referred to as a "wildcard." The search will return results that include various endings or suffixes. In the example below, using the wildcard educat* will return results that use the terms education, educator, educated, educate, or educating.

Using truncation is especially useful when you are looking for both the singular and plural forms of a word. For example, searching for teacher* will yield sources that mention "teacher" in the singular as well as "teachers." You can place your asterisk within a word to search for different kinds of plurals or spellings.

While most databases and search engines use * for their wildcard, some do not and may use an exclamation point (!) instead. Consult the Help section of the database you are using to determine what symbol they use for wildcards.