Primary, Secondary, and Tertiary Sources

In academic research, the sources you use to support your arguments are categorized into three levels: primary, secondary, and tertiary. Knowing the difference between these types of sources helps you choose the best evidence for your assignments, evaluate the reliability of your information, and understand how to cite them correctly.

The classification of a source depends on how close the creator of the source was to the event or data they are describing.

1. Primary Sources

A primary source is direct, first-hand evidence or an original record of an event, object, person, or work of art. Primary sources are created during the time period under study, or by someone who directly experienced or witnessed the events. They contain raw, unfiltered information.

Examples by Subject Area

History & Social Sciences: Diaries, letters, speeches, photographs, oral histories, government documents (like census data or legislation), newspaper reports written at the time of the event, and physical artifacts (like clothing or tools).
Sciences: Original peer-reviewed journal articles presenting new experimental results, lab notebooks, raw datasets, patent filings, and clinical trial records.
English & Creative Arts: Novels, plays, poems, paintings, sculptures, films, music recordings, and letters written by the artist/author.

When to Use

Use primary sources when you want to analyze original theories or data, draw your own conclusions about a historical event, or perform close readings of creative works.

2. Secondary Sources

A secondary source interprets, analyzes, evaluates, or discusses primary sources. These sources are created after the fact by someone who did not personally witness or participate in the events or research. They analyze primary evidence to construct an argument, identify patterns, or provide historical context.

Examples by Subject Area

History & Social Sciences: History textbooks, biographies, documentaries, and academic articles or books analyzing historical events.
Sciences: Review articles summarizing recent research in a field, meta-analyses, and science textbooks.
English & Creative Arts: Literary criticism analyzing a novel, reviews of plays or movies, and biographies of artists.

When to Use

Use secondary sources to get background context, see what expert scholars have written about your topic, and support your arguments with established research and analysis.

3. Tertiary Sources

A tertiary source indexes, digests, compiles, or summarizes information from primary and secondary sources. They do not contain original research or unique analysis. Instead, they provide a high-level overview of a topic.

Examples

Encyclopedias (like Wikipedia or Britannica), dictionaries, almanacs, directories, bibliographies, and indexing databases.

When to Use

Use tertiary sources at the very beginning of your research to get a broad overview of your topic, identify key terms and figures, and find references to primary and secondary sources.

💡

The Wikipedia Rule: Do not cite Wikipedia (a tertiary source) in your final assignments. Instead, scroll to the bottom of the Wikipedia page and look at the "References" or "External Links" sections. Use those links to find the primary and secondary sources that Wikipedia used, read them yourself, and cite those instead.

Quick Comparison Table

Feature	Primary Sources	Secondary Sources	Tertiary Sources
What is it?	Direct, original evidence or first-hand records.	Analysis, interpretation, or evaluation of primary evidence.	Summaries, compilations, or indexes of other sources.
Creator's Role	Witness, researcher, or creator of the work.	Researcher analyzing someone else's work or events.	Compiler organizing existing information.
Key Questions to Ask	Does this represent original data, a first-hand account, or the creative work itself?	Does this analyze, critique, or summarize primary evidence to build an argument?	Is this a broad collection or summary of facts with no new analysis?
Academic Value	High (provides direct evidence).	High (provides context, analysis, and expert debate).	Low for citations (best used for background reading and finding sources).

Classification Requires Context

The boundary between source types is not always rigid. The exact same document can be primary, secondary, or tertiary depending on how you are using it in your research.

Example 1 (A High School Textbook):
- If you are writing a history paper on the War of 1812, a modern Canadian history textbook is a secondary source (or tertiary source) because it analyzes and summarizes primary sources from 1812.
- However, if you are writing a paper on how the teaching of history has changed over time, a history textbook published in 1950 is a primary source because it is direct evidence of 1950s educational practices.
Example 2 (A Newspaper Article):
- A newspaper article reporting on the signing of the Treaty of Versailles in 1919 is a primary source for a history student studying World War I peace negotiations.
- A newspaper article written in 2019 reflecting on the legacy of the Treaty of Versailles is a secondary source because it analyzes the event from a distance of 100 years.

Determining a Source's Type

If you are struggling to classify a source, ask yourself these three questions:

Did the creator of the source witness or participate in the event, or conduct the original experiment?
- Yes: It is likely a primary source.
- No: It is likely a secondary or tertiary source.
Does the source offer a brand-new analysis, or does it summarize existing knowledge?
- New Analysis: It is a primary or secondary source.
- Summary/Collection: It is a tertiary source.
What is my research question?
- If the source is the object of your analysis (e.g., you are analyzing the language of a 1980s advertisement), it is a primary source for your paper, even if it was originally created as a compilation.