Primary, Secondary, and Tertiary Sources

When searching for information on a topic, it is important to understand the value of primary, secondary, and tertiary sources.

Primary Sources

Primary sources allow researchers to get as close as possible to original ideas, events, and empirical research as possible. Such sources may include creative works, first-hand or contemporary accounts of events, and the publication of the results of empirical observations or research. A primary source is an original document containing firsthand information about a topic.

In the humanities and social sciences, primary sources are the direct evidence or first-hand accounts of events without secondary analysis or interpretation. A primary source is a work that was created or written contemporary with the period or subject being studied. 

In the sciences, primary sources are documents that provide a full description of the original research. This makes them the best source of information on cutting-edge topics. However the new ideas presented may not be fully refined or validated yet. For example, a primary source would be a journal article where scientists describe their research on the genetics of tobacco plants.

Secondary Sources

Secondary sources analyze, review, or summarize information in primary resources or other secondary resources. Even sources presenting facts or descriptions about events are secondary unless they are based on direct participation or observation. Moreover, secondary sources often rely on other secondary sources and standard disciplinary methods to reach results, and they provide the principle sources of analysis about primary sources. A secondary source contains commentary on or discussion about a primary source. Its most important feature is that it offers an interpretation of information gathered from primary sources.

In the humanities and social sciences, secondary sources analyze or interpret historical events or creative works.

In the sciences, a secondary source would be an article commenting on or analyzing the research on a topic. Secondary sources tend to summarize the existing state of knowledge in a field at the time of publication. They are good for comparing different ideas and theories and examining how they may have changed over time.

Tertiary Sources

Tertiary sources provide overviews of topics by synthesizing information gathered from other resources. Tertiary resources often provide data in a convenient form or provide information with context for interpretation.

In the humanities and social sciences, tertiary source present summaries or condensed versions of materials, usually with references back to primary and/or secondary sources. They can be a good place to look up facts or to get a general overview of a subject, but they rarely contains original material.

In the sciences, tertiary sources present condensed material, generally with references back to primary and/or secondary material. They can be a good place to look up data or to get an overview of a subject, but they rarely contain original material.

The distinctions between primary, secondary, and tertiary sources can be ambiguous. An individual document may be a primary source in one context and a secondary source in another. Encyclopedias are typically considered tertiary sources, but a study of how encyclopedias have changed on the Internet would use them as primary sources. Time is a defining element.

While these definitions are clear, the lines begin to blur in the different discipline areas.

Examples (Humanities and Social Sciences):

Examples (Sciences):