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Types of Sources

Primary, Second, and Tertiary

As you conduct research, you will consult different sources of information. A professor may request primary, secondary, or tertiary sources. What does that mean? This guide explains these terms and gives examples for each category.

Primary Sources

Primary Source
Primary Source
Primary Source
Primary Source

Primary sources are original materials. They are from the time period involved and have not been filtered through interpretation or evaluation. Primary sources are original materials on which other research is based. They are usually the first formal appearance of results in physical, print or electronic format. They present original thinking, report a discovery, or share new information.

Examples include:

  • Artifacts (e.g. coins, plant specimens, fossils, furniture, tools, clothing, all from the time under study)
  • Audio recordings (e.g. radio programs)
  • Diaries
  • Internet communications on email, listservs
  • Interviews (e.g., oral histories, telephone, e-mail)
  • Journal articles published in peer-reviewed publications
  • Letters
  • Newspaper articles written at the time
  • Original Documents (i.e. birth certificate, will, marriage license, trial transcript)
  • Patents
  • Photographs
  • Proceedings of Meetings, conferences and symposia
  • Records of organizations, government agencies (e.g. annual report, treaty, constitution, government document)
  • Speeches
  • Survey Research (e.g., market surveys, public opinion polls)
  • Video recordings (e.g. television programs)
  • Works of art, architecture, literature, and music (e.g., paintings, sculptures, musical scores, buildings, novels, poems)
  • Web site

For more detailed information on how to find primary sources in our library see the Primary Sources Research Guide.

Secondary Sources

Secondary sources are less easily defined than primary sources. Generally, they are accounts written after the fact with the benefit of hindsight. They are interpretations and evaluations of primary sources. Secondary sources are not evidence, but rather commentary on and discussion of evidence. However, what some define as a secondary source, others define as a tertiary source. Context is everything.

Secondary Source
Secondary Source

Examples include:

  • Bibliographies (also considered tertiary)
  • Biographical works
  • Commentaries, criticisms
  • Dictionaries, Encyclopedias (also considered tertiary)
  • Histories
  • Journal articles (depending on the disciple can be primary)
  • Magazine and newspaper articles (this distinction varies by discipline)
  • Monographs, other than fiction and autobiography
  • Textbooks (also considered tertiary)
  • Web site (also considered primary)

Tertiary Sources

Tertiary sources consist of information which is a distillation and collection of primary and secondary sources.

Tertiary Source
Tertiary Source

Examples include:

  • Almanacs
  • Bibliographies (also considered secondary)
  • Chronologies
  • Dictionaries and Encyclopedias (also considered secondary)
  • Directories
  • Fact books
  • Guidebooks
  • Indexes, abstracts, bibliographies used to locate primary and secondary sources
  • Manuals
  • Textbooks (also be secondary)

Comparison across the disciplines

SUBJECT PRIMARY SECONDARY TERTIARY
Art Painting by Manet Article critiquing art piece Art museum guide
Chemistry/Life Sciences Einstein's diary Monograph on Einstein's life Dictionary on Theory of Relativity
Engineering/Physical Sciences Patent NTIS database Manual on using invention
Humanities Letters by Martin Luther King Web site on King's writings Encyclopedia on Civil Rights Movement
Social Sciences Notes taken by clinical psychologist Magazine article about the psychological condition Textbook on clinical psychology
Performing Arts Movie filmed in 1942 Biography of the director Guide to the movie


Librarians at the University of Maryland were the authors and inspiration for the material. Original webpage: http://www.lib.umd.edu/ues/guides/primary-sources