What is Boolean searching?
Imagine looking for books about gardens in children’s stories. A search for gardens might bring back far more than you need, while a search for one exact title could miss useful books. Boolean searching gives you a way to tell a search tool how your ideas fit together. Its three basic operators are AND, OR and NOT.
These operators are most useful in library catalogs, article databases and other search tools that support them. Not every tool interprets them in the same way: some assume AND between words, some provide separate search boxes, and some treat ordinary words differently from operators. If a search behaves oddly, check the tool’s help page or advanced-search options. The examples below show the general logic, not a promise that every website will produce identical results.
AND narrows your search
Use AND when a result should contain both ideas. A search for gardens AND fiction asks for results connected to gardens and fiction. It generally returns fewer results than searching either term alone, because each result must meet both conditions. AND is handy when your first search is too broad: start with a subject, then add another idea that matters to you.
Choose each added word with care. Children AND gardens AND poetry may be useful if you want poems about gardens for children, but adding too many conditions can leave out relevant material described in different language. If the results become sparse, remove one term or try a broader word. Searching is often a process of adjustment rather than a single perfect command.
OR makes room for alternatives
Use OR when either term would suit your purpose. For example, bicycle OR cycling can find results that use one word, the other, or both. This generally widens a search. OR is especially helpful for related words, alternate spellings and different names for the same idea. Someone exploring stories about small dwellings might try cabin OR cottage rather than guessing which term a cataloger used.
Think of OR as a way to gather possible vocabulary before narrowing the subject. It does not mean the words are interchangeable in every context. If you search myths OR legends, you may find material about both as well as material focused on only one. Look at a few results to see whether your alternatives are bringing in the kinds of items you hoped to find.
NOT sets something aside—with a catch
Use NOT to exclude results containing an unwanted term. If you are interested in books about jaguars as animals, jaguar NOT car might reduce results about vehicles. This can be useful when one word has several meanings and an unrelated topic keeps dominating your results.
Be cautious, though. A useful book about wildlife might mention cars in its description and disappear from that search. NOT cannot judge whether a result is relevant; it only follows the exclusion rule supported by the tool. Before excluding a term, try adding a positive one instead, such as jaguar AND wildlife. If you do use NOT, compare the results with and without it so you can see what might have been lost.
Put the pieces together
Suppose you want reading about libraries in novels for young readers. You could begin with libraries AND fiction. If you see that relevant records use both library and libraries, try (library OR libraries) AND fiction. Parentheses group the alternatives, telling a tool that supports them to consider either word before combining that group with fiction. Without parentheses, a tool may interpret a longer search differently than you intended.
You can refine the search after looking at the results. If many items are about building design rather than stories, add a useful term such as children: (library OR libraries) AND fiction AND children. If that leaves too little, take children away and use the catalog’s audience filter, if one is available. A phrase in quotation marks, such as "school library", may also help in tools that support phrase searching, but it can miss records that phrase the idea another way.
The simplest habit is to change one thing at a time. Start with two or three important words, scan the titles and descriptions, and notice the language they use. Add AND to focus, OR to include alternatives, and NOT only when an unwanted meaning persists. The goal is not an impressive-looking search string. It is a manageable set of results that helps you discover something worth reading.
