Boolean operators are the words “AND, OR, and NOT”. These simple words can be used in combination with your keywords to broaden or narrow your search results. Let’s take a look at how they work:
You can use the word AND to combine keywords and make your search more specific. For example, if I search for autism AND therapy, the words “autism” and “therapy” would appear in every search result.
You can use the word OR to combine synonyms. For example, if I search for “autism spectrum disorder” OR “autism spectrum condition”, then my results would contain either phrase, broadening my search. This is helpful when your topic is closely related to other topics, when you’re not getting a lot of search results, or when there are many different synonyms that authors might use to describe a concept.
When you write ‘OR’ statements, be sure to enclose them in parentheses. This will make it clear to the database how you want your search terms combined. For example:("autism spectrum condition" OR "autism spectrum disorder") AND therapy
Occasionally you’ll find that you’re getting a lot of irrelevant results around one particular topic. For example, if you were researching autism but you kept getting results related to misinformation about vaccines as a cause, you could use the boolean operator ‘NOT’ as a quick way to filter out those irrelevant results. In this example, you could try adding a ‘NOT vaccine’ to the end of your search string. We recommend using ‘NOT’ sparingly, as you may accidentally filter out results that match your topic.
Note that in our examples, the boolean operators are written in all capital letters. Some databases require this and some don’t, so it’s a good practice to write them in all capitals just in case. Most databases also allow you to choose Boolean operators from a dropdown menu. This gives you another way to build a Boolean search Either method is effective, so choose the one that works best for you!
You can use Boolean operators to build complex search strings that return specific, relevant results. Our search string might look like:
(“Autism Spectrum Disorder” OR “Autism Spectrum Condition”) AND (“cognitive behavioral therapy” OR CBT) NOT vaccine
Remember that searching is an iterative process, so you can adjust this search string as you go. If you find too few results, try adding alternate keywords to the search using OR. If you find too many results, consider eliminating some of your less specific search terms.
Boolean search terms are not the only tools at your disposal! Check out our Tips & Tricks video series for more help or Ask a Librarian!