Boolean operators use a combination of AND, OR, NOT, and parentheses to search databases. Another box on this page has some generic information and examples about using them, drawn from examples that are tried and tested in library databases and Google Scholar. Here, I will showcase how these operators can apply to a search in the LLBA, the Linguistics and Language Behavior Abstracts.

AND

In a database, the AND operator limits results to only return items that contain both of the terms. In the diagram, "both" is indicated in dark blue.

Practically, we can see this in the LLBA. Only 37 items in the database have both the phrases "nonsense syllables" and "nonsense words." noft means not in full text; this ensures that the papers in our results are actually about the terms we are looking for.

OR

The OR operator includes anything that matches either term.

For a concrete example, there are 2,441 results that contain either "nonsense words" or "nonsense syllables."

NOT

The NOT operator removes something from the results. Here, we will see all results that do not contain "nonsense words."

Above, we can see the results.

Boolean searching allows you to customize how you search for things in academic databases, and it's based on a few key pieces of syntax: AND, OR, NOT, (), and "". 

AND

When you put two terms into an academic database, AND is usually implied: You usually want both words in fluid inclusions to appear in your search results. You could just as easily write:

fluid AND inclusions

OR and ""

But let's say that I want to find something about extrasolar planets. However, there was a terminology change around 2007, after which people started using the term exoplanets. If I want articles from both eras, I can do the following:

exoplanets OR "extrasolar planets"

What this tells my database is that I don't care which term appears in the results. I just want one of them. In addition, I want extrasolar planets to be searched as a phrase. (This also works in Google with song lyrics.)

NOT

What if I'm looking for women in STEM (science, engineering, mathematics, and technology) fields, though? Try it. You'll see a lot of resources on stem cells. This is where the NOT operator is helpful:

women stem NOT cell NOT "clinical trial" NOT "stem cells"

Of course, Google and Google Scholar work differently. Instead of NOT, use a - to make it look like this:

women stem -cell -"clinical trial" -"stem cells"

Everything and ()

Or, of course, we could do this with everything (and here parentheses signify order of operations):

women AND ("stem" OR science) NOT cell NOT "stem cells"