A keyword search uses natural language to search for a word anywhere in a record: the title, abstract, subject headings, author, text, etc. (the equivalent of searching "everything" in the library catalog). For example, if you search for fast foods and teenage obesity, you'll retrieve results in which all of these four words appear anywhere in the record at least once. However, you won't find articles that use synonyms of these words, such as overweight or youth.
A subject heading search uses the database's own pre-determined vocabulary. This requires you to know which terms have been assigned for certain subjects. For example, if you want to find articles on fast foods and teenage obesity in Academic Search Premier, you'll need to search for convenience foods and obesity in adolescence. This will retrieve all articles that have been assigned these subject headings, even those that use different wording in the text itself.
|Keyword vs. Subject|
|Natural language words describing your topic. A good way to start your search.||Pre-defined "controlled vocabulary" assigned to describe the content of each item in a database or catalog.|
|More flexible for searching. You can combine terms in any number of ways.||Less flexible. You must know the exact controlled vocabulary word or phrase.|
|Database looks for keywords anywhere in the record (title, author name, subject headings, etc.).||Database looks for subjects only in the subject heading or descriptor field, where the most relevant words appear.|
|Often yields too many or too few results.||If a subject heading search yields too many results, you can often select subheadings to narrow the search.|
|Often yields many irrelevant results.||Results are usually very relevant to the topic.|
There are three little words that are used as Boolean operators: AND, OR, and NOT.
Think of each keyword as having a set of results that is connected to it. These sets can be combined in different ways to produce different sets of results. You can also exclude certain sets from your results. The table below explains how Boolean operators work.
|AND combines different terms when both must be present. Use AND to narrow a search.|
|OR combines terms when at least one must be present. Use OR to broaden a search.|
|NOT eliminates irrelevant terms from a search. Use NOT when you want to exclude all records that contain a certain term.|
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