In library an information science, historiography and some other areas of scholarship, a secondary source is a document or recording that relates or discusses information originally presented elsewhere. A secondary source contrasts with a primary source, which is an original source of the information being discussed. Secondary sources often involve generalization, analysis, synthesis, interpretation, or evaluation of the original information. Primary and secondary are relative terms, and some sources may be classified as primary or secondary, depending on how it is used. Secondary sources include textbooks, encyclopedias, biographies, and web sites.