Use AND to connect words that must appear in a document. This *narrows* your search.
"history of ideas" OR "history of knowledge"
Use OR if only one word must appear in a document. This *broadens* your search.
romantic*
Use an asterisk to truncate a word and allow for different endings, for example, romantic, romantics, romanticism, etc.
"chaos theory"
Use quotation marks to enclose a phrase or words that must appear together in a document.
hermitage NOT museum
Use NOT to exclude words or terms from a search. (If you're looking for articles on a hermitage in a landscape garden, you don't want articles on the Hermitage museum in St Petersburg.)
Library Guides -- and Subject Guides in particular -- can help you choose databases that are relevant to a specific disciplinary approach. There is a Subject Guide that corresponds with each Whitman major.