In biological databases, such as BasicBiosis and PubMed, entering a simple phrase may not be the best way to search. Unlike search engines, many databases will treat a string of keywords as a specific phrase. To combine your keywords and phrases, you need to use what are called Boolean operators.

Boolean operators are simply the words AND, OR, and NOT. They help you broaden (find more) or narrow (find fewer, more relevant) your search results.

The Boolean operator AND helps combine keywords and phrases to find where the terms intersect. The AND operator narrows your search to retrieve only those articles containing both the phrase biological weapons and the word anthrax.