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Research Guides

Information Literacy & Library Research: Keywords and Boolean Logic

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.

Keyword vs. Natural Language Searching 

Searching the library databases is not like searching google. Google uses artificial intelligence to refine your search, anticipating what you are searching for. Searching Google you are able to type in a sentence the way you would speak (natural language searching) and get relevant results. Databases require the use of keywords and logic to search their collections. Databases are not as smart as Google, and will take whatever you type into the search box literally. Databases typically do not understand natural language searches. 

This guide will give you more details on how to use keywords and Boolean logic to create your database 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 about database searching, and you will have to create several different database searches using keywords and Boolean operators (AND, OR, and NOT). 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 punctuation marks and symbols, such as parentheses and asterisks in Academic Search Ultimate or ProQuest Central.


Searching a Library Database is a lot like online shopping, because you have to type in exactly what you need. You must first identify some good keywords to use in your search. 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 won't be helpful as keywords because they are only embellishing the nouns or verbs and should probably not be used at all. 

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

Mental health
College students

When you have a keyword that contains multiple words (also called a keyphrase), such as “mental health,” you should consider putting quotation marks around the keyphrase to keep the words together (see section on Quotation Marks below).

Synonyms of Keywords

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. This is because scholars study very specialized topics and they use specialized language to describe what they are looking at. For example, instead of bird songs, researchers in ornithology might study bird calls or bird vocalizations. 

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 “stress-reduction” 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 keyword bank. 

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 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:  In many databases the AND is implied, but not all of them. Google automatically puts AND between search terms. However, they are not always connected in the way that you intend. 

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 (see section on Quotation Marks below).

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: If you use AND and OR operators in a search, you must enclose the words that are connected together with OR in parentheses (See section on Parentheses below).

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 keywords that may be implied by your search terms, narrowing your search
  • example:  media NOT internet

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

Warning: Be very careful when using NOT. You may miss out on relevant information. It is especially tricky when combined with other boolean operators. Only use it when your search results are “contaminated” by a certain keyword. For example, when you are searching for articles on stress and you keep getting articles about stress fractures, you can search stress NOT fractures. 

Punctuation Marks and Symbols


Quotation Marks

Quotation Marks will keep phrases together as a unit. This means that whatever is inside the quotation marks will be searched with that exact order and spelling. When using keywords of more than one word, think on whether it is important to keep those keywords together in that exact order and spelling. Quotation marks ensure that the words will be kept together, in that specific order. 

For example, phrases like “mental health” or “high school” will lose their meaning if you split it up into individual words or if you change the order of the words. 

The phrase “college student” is different because there are many ways to refer to college students so it matters less if those words appear in that order. So when making decisions as to when to use quotation marks, it  could look like this:

“Mental health”
College students

Never put quotation marks around long phrases or parts of sentences. Since the database will only look for that exact specific sentence snippet or phrase in that exact order it may reduce your results depending on how unique the phrase is. Searching with a unique phrase may give you no results. The only time when you would use quotes is if you are looking for a specific title and there are a lot of commonly used words in that title.

If you are unsure as to whether you should use quotation marks around your keywords, try it with and without and see what gives you more relevant results, or if it narrows your results too much. Remember, searching is trial and error. 


Parentheses go around OR statements to keep them together as a unit and to show the system that the terms between the parentheses are interchangeable.

For example: (fear OR anxiety OR worry OR distress) AND cancer patients.


Asterisks and Question Marks

Asterisks are a shortcut to capture different variations of a keyword. For example, tobacco AND adolescen* is a quick way to search for tobacco AND (adolescent OR adolescents OR adolescence). The asterisk allows the ending of the word to vary. You truncate the word at any letter except for the first. Using an asterisk is called truncation searching. 

The question mark does the same thing as the asterisk but for a single character only. It is handy to use for spelling variants. For example job AND speciali*ation is shorthand for  job AND (specialisation and specialization), capturing both the British and American spellings. Using a question mark to replace a single character is called wild-card searching.