In 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; a primary source can be a person with direct knowledge of a situation or a document created by such a person.
A secondary source is one that gives information about a primary source. In this source, the original information is selected, modified and arranged in a suitable format. Secondary sources involve generalization, analysis, interpretation, or evaluation of the original information.
The most accurate classification for any given source is not always obvious. Primary and secondary are relative terms, and some sources may be classified as primary or secondary, depending on how they are used. A third level, the tertiary source, such as an encyclopedia or dictionary, resembles a secondary source in that it contains analysis, but attempts to provide a broad introductory overview of a topic.