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Online Searching

Dogs and Cats

Dogs or Cats

Dogs not Cats

Boolean Searching

Boolean Searching, sometimes called Keyword Searching, combines multiple search terms using the words AND, OR, and NOT.

Dogs AND cats - Finds only documents that contain both words. It ignores documents that contain only Dogs or only Cats.

Dogs OR Cats - Finds all documents that contain dogs AND all documents that contain Cats - a much larger result than Dogs and Cats.

Dogs OR Cats - Finds all documents that contain Dogs, but eliminates any dog documents that also contain Cats.



1. The more search terms the fewer the results.

  • Dogs - Finds many.
  • Dogs and Cats find fewer.
  • Dogs and Cats and Birds finds even less.
  • Dogs and Cats and Birds and Leopards and Elephants and Goats may find nothing.

2. The fewer search terms the greater the results.

  • If you don't find enough under Dogs and Cats and Birds, try just Dogs and Cats.

3. Expand your search using Or. Think of similar terms and combine them with your original term.

  • Dogs or Canines or Pet

4. Use Not to eliminate unwanted results. For instance, if you are trying to find information about Dolphins but you keep getting results about the Miami Dolphin football team, try this.

  • Dolphins not Miami

Try Boolean Searching

Go to the Library Catalog and compare the number of titles retrieved in each of the examples listed under Rules 1, 2, and 4.

Boolean Searching in Google


  • You do not need to use AND. It is implied.
  • All phrase searching is really AND searching in Google.
  • "The effect of alcohol on driving" is interpreted by Google's search engine as
  • effect AND alcohol AND driving


  • Add + to a word to require its presence
  • Example "The +effect of alcohol on driving" requires the presence of the work "effect."


  • Add - to a word to require its absence
  • Example: -Miami dolphins (will find dolphins, but not Miami)


  • Place a phrase in quotes to require the presence of each word in that exact order.