Is the date of a famous historical event common knowledge?

Yes. Widely accepted dates, such as the signing of the Declaration of Independence on July 4, 1776, are considered common knowledge and do not require a citation.

Does common knowledge change based on the audience?

Yes. Information considered common knowledge in a professional medical journal may require a citation in a general high school essay. Always consider the expertise of your readers.

What if I didn't know the fact before I read it in a book?

If the fact is easily found in five or more independent general reference sources, it is still common knowledge even if it is new to you personally.

Are scientific theories common knowledge?

Established theories like gravity or evolution are common knowledge. However, specific recent data, niche studies, or new interpretations of those theories must be cited.

What is Considered Common Knowledge?

Explainer4 min·Updated May 2024

Definition of Common Knowledge

Common knowledge refers to information that the average reader can find in multiple sources or is widely known by a specific audience. In academic writing, common knowledge does not require a citation because the facts are undisputed and not the intellectual property of a specific individual or organization.

Common Knowledge vs. Citable Information

Comparison Criteria

Feature	Common Knowledge	Citable Information
Goal	State undisputed facts	Attribute unique ideas or data
Origin	General public domain	Specific authors or researchers
Evidence	None required	In-text citation and bibliography
Tone	Factual and foundational	Analytical and evidence-based
Frequency	Found in 5+ general sources	Found in specific niche studies
Subjectivity	Objective and non-controversial	Opinionated or interpretative

What Qualifies as Common Knowledge?

Common knowledge generally falls into two categories. The first is universal common knowledge, which includes facts like 'the Earth orbits the Sun' or 'Washington D.C. is the capital of the United States.' These are facts that almost any adult knows or can find in a basic dictionary or encyclopedia. The second category is field-specific common knowledge. This includes information widely known within a specific discipline, such as 'mitochondria is the powerhouse of the cell' in a biology paper. If you are writing for experts, you do not need to cite foundational concepts they already accept as true.

The Risk of Plagiarism

Plagiarism occurs when you present someone else's unique ideas, interpretations, or specific wording as your own. While you do not need to cite that George Washington was the first U.S. President, you must cite a historian's specific argument about why his leadership style was effective. Failing to distinguish between a general fact and a scholar's unique analysis is a frequent cause of accidental plagiarism in student essays.

Common Knowledge vs. Citable Content Examples

Example

Review these examples to see how the distinction applies to real essay content.

**Example 1: History**
* **Common Knowledge:** World War II ended in 1945.
* **Citable:** 'The economic recovery of post-war Germany was primarily driven by the currency reform of 1948 rather than the Marshall Plan alone' (Smith, 2022).

**Example 2: Science**
* **Common Knowledge:** Water freezes at 0 degrees Celsius.
* **Citable:** 'Recent samples from the Arctic shelf indicate a 12% increase in microplastic concentration over the last decade' (Environmental Research Group, 2023).

The 'Five Source' Rule

If you are unsure if a fact is common knowledge, apply the five source rule. Look for the information in five different independent sources, such as general encyclopedias or introductory textbooks. If all five sources mention the fact without citing a specific study or author, it is likely common knowledge. However, if you are still in doubt, the safest path is always to provide a citation.

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