Skip to Main Content
Decorative SUU library logo

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

Unlike Google, which uses artificial intelligence to filter and refine your searches for you, guessing at what you mean and making mistakes, the databases used at the library are much more basic. They are fast and not fancy or smart. They use logic and keywords to search their vast collections to give you the results, and they will take whatever you enter into the search box literally.

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

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. Having a clear understanding of what each operator does and how it affects the scope of your results will help you in your searching a lot. 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.

Keywords and Boolean Operators


Keywords summarize your topic without using a lot of words. Most basic search engines work better with keywords, such as when you are shopping online. Think of what words you would search for if you were buying a pair of shoes. Would you type in a whole sentence, or just put in the words that describe the item?

For example, If you were looking for a pair of running shoes, where would you look for them? What words would you use to narrow the search?

You might search reviews for the best running shoes first, or you might just go to the website of your favorite shoe store. When searching for those shoes on the store’s website, you might put in “running shoes,” possibly adding your size, favorite brand, or even color.


I want to buy new running shoes.

Keywords: running shoes

Narrow it down by adding size, brand, color, or style

Women’s running shoes, Nike, blue, etc.

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, where you would put your research question directly into the Google search bar, library databases use keywords and logic to search database content.

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 won't be helpful as keywords because they are only embellishing the nouns or verbs and should probably not be used at all. 

The main elements in your research question (such as the 3 elements: person(s)/place/ thing, cause, and effect) are examples of keywords with specific roles in your research question. Once you have a simple but good question, you can easily pull your starting keywords from it. 


Question: How can dogs improve the mental health of college students?
Main Points: How might dogs (cause) influence the mental health (effect) of college students (persons)?
Keywords: dogs AND "mental health" AND "college students"

It is best to put quotes around multiple words to keep them together, so that the database knows they are one key phrase instead of two separate keywords that mean something different when they are searched separately (mental and health are not the same things as "mental health" as a united concept. Likewise, searching animal AND rights might bring up anything that mentions animal and mentions rights, but searching "animal rights" links them together as a single multi-word phrase).

But choosing your keywords isn’t as simple as just pulling out the words you think describe your topic. Often there is a different vocabulary that the researchers in that discipline use when talking about your topic. The official terms rather than the vernacular. It is the academic or official terms you want to use as your keywords. An example of this is Marijuana and Cannabis. Both refer to the same plant, but one is a more technical term, and the other is a more informal, commonly used term. Both could work as keywords, but when searching you might see a difference in which type of articles uses which term. Another example of a vernacular versus a technical term is dogs and canines or cats and felines. While dogs and cats can probably be used as keywords just fine, knowing that those technical terms for the same things might be helpful as well. Often those technical terms will be much more helpful when searching the databases, so pay attention as you start researching.

When you did your background research, it helped you figure out what words are more typically used and what the technical terms for your topic are. Pay attention to what words the encyclopedias or background articles use because they can hopefully serve as your keywords. Making lists of the terms you see while doing your background research is very helpful when it comes to this step of database searching.

As you start searching, you can always collect more potential keywords to use on the way. Pay attention to the subjects listed in your results for more ideas for keywords. These lists of subjects are examples of standardized keywords called “subject headings” and they work very similarly to hashtags in social media. Using these subject heading keywords may give you better results because your keywords will be the same words that everyone else is using.

Remember, a keyword is only as helpful if it is used by the people writing your articles, and your goal is to try and find the words that the researchers or scholars writing the articles are using so that you can find these articles in your search.

Boolean Logic and Operators

Boolean is a simple logic (think math with words) that tells the databases how to search the keywords using a series of operators, the most common being AND, OR, and NOT.



AND is the basic and most used of the operators, and tells the database that all the results have to contain the keywords connected with AND. The Boolean operator AND is necessary for ALL of your searches, and should be your go to operator. Using AND will narrow down your results because you are basically asking the system to only find sources that have all the keywords of your search in it, not a subset of them. The more keywords you connect with AND, the more specific your search becomes and, as a result, the smaller the number of results you get back.

The Google Search Engine only uses AND, but it is built in to assume its use so we don’t necessarily know it since we don’t have to type it out. AND should be the operator you use to connect your keywords together to show the database that you want those keywords to appear in your results. The basic search from the example before uses AND to connect the keywords.

dogs AND "mental health" AND "college students"

Please note how the multiple word keywords have quotation marks around them to show they are one “keyword.”

Again, since AND is requiring that all of the keywords connected with it to appear in your results, adding more keywords with AND will always narrow your search and give you less results. The more keywords you add with AND connecting them, the less results you’ll get just based on there having to be more criteria to be found in them.



OR is used if there are multiple ways to say the same thing or if certain keywords can be used interchangeably. By using OR you can search for all the variations of a term at the same time. Words that have commonly used synonyms or different ways to basically say the same thing are prime examples of when to use OR. For example, if you are researching cell phone addiction, you should probably make sure that you will also find articles from Europe where cell phones are called mobile phones or mobiles. Your search will look something like this:

addiction AND (“cell phone” OR “smartphone” OR “mobile phone” OR mobile) 

So you are basically telling the system, my results need to be about addiction and cell phones, whether they are called cell phones, mobiles or smartphones in the article, I don’t care. In doing so you are giving the system more options to search for, and the number of results will likely increase.

But you have to be careful when using OR because it only becomes helpful when the words or terms are all similar in meaning, representing the same concept. For example,  the following search, Dogs OR “mental health”, your results would have articles about just dogs with nothing to do about mental health and articles about mental health with no mention of dogs, and articles with both mixed in. The Boolean operator OR should only be used for terms that are interchangeable, or mean basically the same thing, so it doesn't matter if only one is used.

For example, Dogs and Canines are two words for basically the same thing, and researchers might use either one, so if you are doing a search and want to make sure you cover all your bases, you could potentially do the search:

(dogs OR canines) AND "mental health"

Parentheses are used around OR terms to group keywords together (just like in the order of operations in math) so that the database only applies the OR to those keywords that are equivalent and belong together.

Basically, using OR is a shortcut for doing multiple searches at the same time. Searching (Dogs OR Canines) and "Mental Health" is effectively searching at the same time:

(Dogs AND "Mental Health")


(Canines AND "Mental Health")

To reiterate, because it's combining multiple searches into one search, OR will broaden your search, giving you more results, because it catches all the articles that include one or more of the suggested keywords in the OR search statement. Remember that you still need to use parentheses for OR statements even if you use the stacked search boxes in Academic Search Ultimate. See below for two examples of how the same OR search might look in Academic Search Ultimate.

Academic Search Ultimate advanced search using the search (dogs OR canines) AND "mental health" in one box.

Academic Search Ultimate advanced search using the search (dogs OR canines) in the first box and "mental health" in the next box with the built in Boolean AND operator.


A good way to discover synonyms or interchangeable terms is with the prediction or suggestion feature in Academic Search Ultimate. When you start typing in your keywords, it will sometimes suggest some OR keywords. Those are good examples of the types of terms you are wanting to use. They are not the vernacular terms we use in everyday language, they are the scholarly terms the researchers will use in their writing.

A search in Academic Search Ultimate showing the predictor function, suggesting potential synonyms for "mental health"



NOT is ONLY used when you want to exclude a keyword from your results, such as in the case of homonyms, or when the same spelling of a word means different things. Such as when you are researching mental stress, but your results keep talking about broken bones, or stress fractures. 

Stress NOT Fracture

NOT will narrow your search because it will eliminate any results that contain the keyword after it. However, be very careful when using it, because it can accidentally  eliminate results you actually do want because the term you do not want to see in your results is present in sources that are actually relevant.

For example, the word “pilot” means someone who flies an aircraft, but it can also mean a test study, when doing research. So if you were researching pilots, you might find your results have a lot of irrelevant results because pilot study is a commonly used phrase in research articles. If you searched pilot NOT study to get rid of all the “pilot study” results, you might inadvertently get rid of results you do want, namely studies about pilots. 

Three venn diagrams showing the results of the three Boolean Operators AND, OR, and NOT.