Refining Google Searches with the Inclusion and Exclusion Operators
Using simple Google operators (symbols), such as inclusion and exclusion, can improve web search results without much effort. Operators are used with Google search terms and have a special meaning to Google. They are not included in the subject of a search, but rather change how Google works when it performs a search.
The inclusion operator
The inclusion operator, signified by a plus sign (+), forces Google to include the indicated word on each page that is returned as a result. The inclusion operator, +, must come immediately before the term to be included, without any spaces.
The inclusion operator is most useful for reinserting the stop words that Google leaves out by default. Sometimes you really need to include stop words to get the best results. Never fear; the + is here. For example, if you search for
Star Wars I
the results omit I from the search results. (In fact, Google even displays a message to let you know that I is a very common word and was therefore omitted from the search.) If you're really looking for results related to the first episode of the Star Wars space opera, it's handy and dandy to be able to enter
Star Wars +I
and get search results related to Episode I: The Phantom Menace.
The exclusion operator
The exclusion operator requires Google to return results that do not include a specified term. This operator is represented by a minus sign (–) before the term to be excluded (no spaces are allowed between the operator and the excluded term).
Exclusion is one of the most useful operators a researcher can use because it allows you to clarify the context of terms. Many words are used across a number of fields. For example, a virus can infect a computer or a person. A search for
should, in theory, show only biological viruses. If you try this search, you'll see that in fact it includes biologic viruses, philosophic pseudo-religious viruses, and more, as well as some computer virus links. In contrast, a search just for virus returns primarily links about computer viruses. So the exclusion operator doesn't always work perfectly, but it does improve results.
Here's another example. Take the search term fly. Fly could refer to an insect, fishing, a kind of guy, or an airline. Suppose your research interest is in the fly genome. You can suppress a great many extraneous results using the exclusion operator in a search such as this:
fly -guy -airplane -airline -fishing
Of course, you can combine multiple terms along with exclusion operators. This technique is likely to give you better results than just using exclusion operators (the inclusion operator is implied when you add any new term to your query).
For example, if you want to find biological but not computer viruses, using a search term that includes virus and biological and excludes computer, like this,
virus biological -computer
is a good idea. If you are looking for the fly genome, you'll get pretty good results if you include both fly and genome in your search. (There's really not much point in excluding guy, airplane, airline, and fishing as shown in the previous section because these terms don't come up in search results when you add the term genome to the mix.) But you might want to search for fly genomes that belong to flies other than the fruit fly. If so, you could include genome and exclude fruit, with excellent results:
fly genome -fruit