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Research Guides

Information Literacy & Library Research: Keywords and Boolean Operators

Information literacy is the ability to know when information is needed and to be able to identify, locate and evaluate, and then legally and responsibly use and share that information.

Database Searching Logic

Keyword vs. Natural Language Searching 

Searching the library databases is not like searching Google. Google uses a combination of search algorithms to refine your search and get the best results possible. Most people are unaware of this as it happens in the background. This is why most people who use Google think they are very good at searching, but Google is just very good at changing their bad searches into good ones. Google also allows you to type in a sentence the way you would speak (natural language searching) and give you relevant results. In contrast, databases require the use of keywords and Boolean logic to search their collections. Databases are not as advanced as Google, and will take whatever you type into the search box literally. If you make a spelling error in a database search, it won't fix it automatically and will return 0 results. Most databases do not understand natural language searches. When you search the library databases, you will have to know how to search as there are no algorithms running in the background to do the work for you.

This guide will give you more details on how databases use keywords and logic to create their searches.

Pro Tip: Google also allows you to search with keywords and logic. This will almost always improve your results. Learn more: Refine Google Searches, but for this module we want to focus on database searching. 

Note for INFO 1010:

The Module 3 assignment is all about database searching, and you will have to create several different database searches using keywords and Boolean operators to combine the keywords together. Having a clear understanding of what each operator does and how it affects the scope of your results will help you in your searching. Pay close attention to how each operator affects your results and how to use the formats, such as parentheses and the different search boxes in Academic Search Ultimate.



Searching a library database is more like online shopping than searching Google, because databases are extremely literal. They are fast, but not smart. Databases will search exactly what you enter, no more, no less. Rather than the natural language we are used to when googling, library databases use keywords and logic to search database content.

For example, if you were looking for a pair of running shoes at an online store, what words would you use to narrow the search?

You might put in “running shoes,” possibly adding your size, favorite brand, or even color.

Keywords are essentially the main points or concepts of your topic or research question. They describe your topic in just a few words. Typically nouns make the best keywords because they are the subjects of your topic. Verbs tend to be less useful, and should only be used sparingly. Adjectives and adverbs are not as helpful as keywords because they are only embellishing the nouns or verbs so it is better to avoid them. 

Sometimes keywords consist of several words that go together. For example, real estate, or Salt Lake City. Quotation marks will keep these phrases together. So when you search you would type in "real estate" or "Salt Lake City".

So if your research question was How might dogs influence the mental health of college students? You would choose the nouns as your keywords:


mental health

college students

Two of our keywords have more than one word. When using keywords of more than one word, you must use quotation marks. Quotation marks ensure that the words will be kept together, in that specific order. So now our keywords should look like this:


"mental health"

"college students"

The next step is to see if there are any important synonyms or other terms that you should use in your search. You don’t want to miss out on any research about dogs simply because the authors are using the word canines. So add canines to your list of keywords. Likewise, what if they are using terms like anxiety or depression, instead of mental health?

Now your keywords are expanding

dogs/ canines

mental health/ anxiety /depression

college students/ university students

As you did your background research, and as you learn more about your topic, you may notice that scholars are using different keywords or subjects in their research. Scholars often use specialized language when talking about their research. When you find a relevant article, look at the keywords or subject terms the authors have identified. You can find these terms by clicking on the title of the article:

It looks like “mental health of students” might be a good one to try that we didn’t even consider.  There are other terms here that might be really helpful as well. Add these to your list of keywords to draw from when you revise your search. 

Remember, a keyword is only helpful if it is used by the people writing the articles, and your goal is to try and find the same words that the researchers or scholars are using. Only with those keywords will you be able to find the articles best suited to your topic. This is what makes database searching challenging, but also fun. Sometimes you have to do some detective work to find the right words. If this is not your thing, you can always ask a librarian for help. 


Boolean Logic and Operators

Boolean logic is a simple logic (think math but with words) that tells the databases how to search with the keywords you provide. The database uses a series of operators, also known as Boolean operators for searching: AND, OR, and NOT. Boolean operators are important because they combine your search words together to either narrow or broaden your results, helping you find what you are looking for.

Example: information literacy (title) AND Armstrong (author) AND 2018 (year)

Using AND

Use AND in a search to:

  • narrow your results

  • tell the databases that ALL the keywords you combine with AND must be present in the results

  • example: "gun control" AND laws AND "United States"

The middle section of the Venn diagram below represents the results set for this search. This search asks the database to find sources that have all three keywords in it. Using AND to combine keywords results in a smaller result because there are only a limited number of sources that have all three keywords. 

Pro Tip:  Google automatically puts AND between search terms, so you do not have to do it yourself. However, sometimes this combines keywords in unintended ways. 

For example, our search above may be translated to gun AND control AND laws AND united AND states. The words could appear individually in any of the resulting articles, not necessarily together.

To compensate for this, it is helpful to use quotation marks around phrases to keep words together and in the order you want them to appear.

Example: “gun control” AND laws AND “United States”

Using OR

Use OR in a search to:

  • connect two or more synonyms (or similar words)

  • tell the database that ANY of your keywords that are combined with OR can be present in the search results

  • example: vegan OR vegetarian OR plant-based

All three circles represent the results for this search. It’s a big set because any of the keywords may appear somewhere in the results using the OR operator, even if they are not relevant to our topic. 

ProTip: You must enclose the words to be "ORed" together in parentheses.

Example: microbiome AND (vegan OR vegetarian OR plant-based). If you don’t use parentheses around the OR statement you will get many, many irrelevant results. 

Using NOT

Use NOT in a search to: 

  • exclude words

  • tell the database to ignore certain keywords that may be implied by your search terms, narrowing your searcH

  • example: bears NOT football

The Venn diagram below shows the results for this search. All of the results about bears are included EXCEPT ones that include the word football. 

Warning: Be very careful when using NOT. You may miss out on relevant information because your source may mention the term you want to exclude only in passing (e.g. grizzly bears hanging out on football fields). It is especially tricky when NOT is combined with other Boolean operators.