22 Information Sources: Primary, Secondary, Tertiary

Information Creation & Context

We can group information sources into three basic categories: primary, secondary, and tertiary. When we make distinctions between these three categories of sources, we are relating the information itself to the context in which it was created. Noting this relationship between creation and context helps us understand the big picture in which information operates, and prompts us to consider whose voices we are including in our research, and whose voices may be left out.

Primary Sources

Primary sources are first-hand observations or experiences of an event. They can also be the original sources of information before they have been analyzed, such as statistical data sets. Examples of primary sources include:

  • Eyewitness reports (interviews, photographs)
  • Speeches, diaries, memoirs
  • Empirical research
  • Original documents, historical newspaper articles
  • Literary works (novels, plays, poems), artworks
  • Tweets
Photograph: Protesters with Causa Justa / Just Cause speak on the steps of San Francisco City Hall for a "Families Belong Together" rally. One holds a sign reading "Las Familias Pertenecen Juntas"
Eyewitness photograph: Protesters speak on the steps of San Francisco City Hall for a “Families Belong Together” rally.

Secondary Sources

Secondary sources are created after an event occurred and offer a review or an analysis of the event; they provide an interpretation of the primary source or data without offering new data. Examples of secondary sources would be:

  • Biographies, nonfiction books
  • Editorials
  • Literary criticism and reviews
  • Periodicals (such as scholarly journals, magazines, or newspapers)
  • Retweets
Cover of nonfiction book, "World of Walls: The Structure, Roles, and Effectiveness of Separation Barriers"
Nonfiction book analyzing the consequences of the construction of physical and virtual walls.

Tertiary Sources

Tertiary sources are compilations of information coming from secondary and primary sources; these can be lists or collections, and are generally reference material that can help you find, or direct you to, secondary and primary sources. Examples of tertiary sources include:

  • Encyclopedias, dictionaries
  • Indexes
  • Databases, catalogs
  • Most textbooks
Wikipedia entry for "Family immigration detention in the United States:
Wikipedia, an online encyclopedia, is an example of a reference source (tertiary)

Note: These categories may differ between subject areas. For details, see section on Information Sources: Traditional Formats.


Creation & Context section adapted from “Primary, Secondary & Tertiary Sources” by Teaching & Learning, Ohio State University Libraries, licensed under CC BY 4.0

Examples adapted from “Library 10” by Cabrillo College Library, licensed under CC BY 4.0

Image: “Families Belong Together SF march” by Pax Ahimsa Gethen is licensed under CC BY-SA 4.0

Image: “World of Walls: The Structure, Roles and Effectiveness of Separation Barriers” by Said Saddiki is licensed under CC BY 4.0



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Introduction to College Research Copyright © by Walter D. Butler; Aloha Sargent; and Kelsey Smith is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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