Q. What are primary, secondary, and tertiary sources?

Primary sources provide firsthand evidence gathered by the author(s).  They may be created or documented at the time of an event, as in scholarly research articles, reports, letters, speeches, diaries, photographs, conference proceedings, and newspaper reports. A primary source may also be  documented at a later time, such as autobiographies, interviews, memoirs, and oral histories...but these are still firsthand accounts. 

• See How can I find primary sources? for search tips.

Secondary sources describe, interpret or analyze information obtained from other sources (often primary sources).  Examples of secondary sources  include many books, textbooks, and scholarly review articles. 

Tertiary sources compile and summarize mostly secondary sources.  Examples might include reference publications such as encyclopedias, bibliographies or handbooks.

Note:

• There are differences between the disciplines in the ways that source types are "typically" defined, though the overall definition above still applies.  In history, for example, "primary source" usually refers to historical documents or artefacts (letters, reports, diaries, photographs, speeches, etc.).  In science, it usually refers to original research studies (where data were gathered and analyzed). In the arts and humanities, it's likely to mean original creative works (paintings, poetry, sculpture, photography, etc.).  Just remember that the key:  primary = original or firsthand.
   
• Defining a source as primary or secondary can also depend on how you are using the material.  For example:
  • A magazine article that discusses recent studies linking artificial sweeteners to health problems would generally be considered a secondary source, because all its information came from other sources. 
  • But, if you were writing a paper on how popular perceptions of artificial sweeteners have changed over time, that magazine article could be considered primary, because it's an example of how public opinion on artificial sweeteners has begun to change. It's a bit like a photograph in that way - it captures a growing opinion in our culture, at a given moment in time.

See Also:

• Primary Source Research on the library website.
• Primary, Secondary, and Tertiary sources in Research@APUS on the library website.  Navigate to the section on Research Fundamentals.