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Primary vs. Secondary Sources

Primary, Secondary and Tertiary Sources

Your professors may require you to use different types of sources for your projects.  How can you identify these?  Basically, this distinction illustrates the degree to which the author of a piece is removed from the actual event being described, informing the reader as to whether the author is reporting impressions first hand (or is first to record these immediately following an event), or conveying the experiences and opinions of others—that is, second hand.

Primary Sources

A primary source provides direct or firsthand evidence about an event, object, person, or work of art. Primary sources include historical and legal documents, eyewitness accounts, results of experiments or research, statistical data, pieces of creative writing, audio and video recordings, speeches, and art objects. Interviews, surveys, fieldwork, and Internet communications via email, blogs, listservs, and newsgroups may also be considered primary sources.

Secondary Sources

Secondary sources describe, discuss, interpret, comment upon, analyze, evaluate, summarize, and process primary sources. Secondary sources are not evidence, but rather commentary on and discussion of evidence.  These materials can be articles in newspapers or popular magazines, book or movie reviews, or articles found in scholarly journals that discuss or evaluate someone else's original research.

When evaluating primary or secondary sources, the following questions might be asked to help ascertain the nature and value of material being considered:

  • How does the author know these details (names, dates, times)? Was the author present at the event or soon on the scene?
  • Where does this information come from—personal experience, eyewitness accounts, or reports written by others?
  • Are the author's conclusions based on a single piece of evidence, or have many sources been taken into account (e.g., diary entries, along with third-party eyewitness accounts, impressions of contemporaries, newspaper accounts)?

Tertiary Sources

Tertiary sources consist of information which is a distillation and collection of primary and secondary sources.  Tertiary sources can be encyclopedias, dictionaries, textbooks, websites, guidebooks, chronologies, manuals, bibliographies, interviews, etc.  (Keep in mind that some of these may also be considered primary or secondary sources depending on the context.)

Ultimately, all source materials of whatever type must be assessed critically and even the most scrupulous and thorough work is viewed through the eyes of the writer/interpreter. This must be taken into account when one is attempting to arrive at the 'truth' of an event.

If you’re not sure about a source or have any questions about using it for your project, don’t hesitate to contact Gwen Cunningham, Science Librarian at or visit any of the librarians in ODY Library.

Click here to take a short (fun!) quiz on determining the difference between primary and secondary sources.