Keywords and Subjects are not the same! Keywords (like how you search Google) are not controlled—just important words and phrases related (sometimes loosely) to the topic. Subject terms or subject headings are what the item is "about"—they are controlled or standardized vocabulary that is used throughout a database and will provide the most relevant resources about the same topic. See the chart below from Dakota Wesleyan University for a great overview of the difference.
Stop words: a, an, are, be, if, in, into, of, on, the, which...these words are excluded and ignored by a database. You can leave them out of any search unless they are necessary. If they are necessary, then you want to put the phrase that includes the stop word(s) within quotation marks to tell the database to include those words in the search.
By using these connectors when employing library searches you will achieve the best results.
Most Databases include a way to search the specific Subject Terms used within that database. Knowing and using the databases own controlled vocabulary will make you the most efficient researcher you can be. When browsing a database for its controlled vocabulary look for a navigational link that says Subjects, Subject Terms, Thesaurus, Index, etc.. The name used may vary but the purpose (a dictionary of the controlled vocabulary) is the same.
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