When you enter the OR operator between two words in your search engine, you are telling it to find documents that contain either word (you don't care which word, just one of them.)

For example, let’s suppose that your students are purchasing a classroom fish tank and they would like to know more about goldfish and guppies. In the search engine, typing in "goldfish OR guppies" (without the quotes) will yield pointers to documents that contain the word "goldfish" or the word "guppies".

Entering AND between two words will yield only documents with that contain both words. In our example above, entering "goldfish AND guppies" (without the quotes) would give your students only documents with both words.

NOT tells the search engine to disregard those documents that contain a word. This is a powerful command and should be used sparingly. For example, if your search about goldfish and guppy food yielded lots of information about swordtails, you might be tempted to try "NOT swordtails". But, what if the utmost authority on goldfish happened to be a swordtail enthusiast? Perhaps her name is Irma Swordtail? You might eliminate the very thing for which you are searching!

In using OR and AND, you can go one step further, using concepts from algebra. Parenthesis can help the search engine determine exactly what you mean. Maybe you want your students to find articles about what the fish eat. If you enter "goldfish OR guppies AND food", you might not get the documents you intend. Your search engine does not read left to right the way humans do. Most interpret the AND first, then follow with the OR. So, in this case you might get information about guppies and food and any information about goldfish.

To solve this dilemma, we can tell the search engine to interpret the OR first by typing " (goldfish OR guppies) AND food" (without the quotes).

Parenthesis are not needed when you are only using AND: "goldfish AND guppies AND food" or only using OR: "goldfish OR guppies OR food".

Yet another way of narrowing your search is to use the term NEAR. This operator will retrieve two words that are close together (each search engine determines the delimits of proximity - five to 10 words perhaps.) A large document can contain many different words, and combining the words can create topics not really sought after. For example, if you were searching for information on gray cats, and searched for"gray AND cats", documents describing cats that lived in gray houses, or slept on gray mats, or woke up and the day was gray might appear on the list. If you enter "gray NEAR cats", you stand a better chance of retrieving what you want.