When researching, you’ll quickly discover that there are all kinds of different resources where you can gather information about your research topic. One of the most important distinctions you’ll need to learn is the difference between primary and secondary sources.

Those words are already suggestive: “primary” probably makes you think of the most important stuff, the material that will take center stage in your project, and “secondary” likely makes you think of the less important stuff—the supporting material that provides background information about the important stuff. That’s mostly true and will usually steer you right, but it turns out to be a little more complicated than that.

Generally, primary sources are those that either ARE an original work or GIVE A FIRST-HAND ACCOUNT of original work, while secondary sources are those that REPORT ON the original works of others.

That general rule is applied differently in different fields. For example, to a historian, the United States Constitution (an original document) would be a primary source, while an academic book that analyzed the Constitution would be a secondary source. In communications, you could make the same distinction between a speech (another primary source) and a critical review of that speech (a secondary source).

In the sciences, because the reader can’t go into the laboratory or the field with the researcher, the original work is the scientific research article published about their research in scientific journals. In these documents, researchers basically tell the reader: “We did these experiments, and these are the results we got and what those results mean.”

Secondary sources in the sciences are books and articles that review, discuss, analyze, and interpret the works of others without presenting any new scientific research.

Examples here would include review articles, which give the reader an overview of a particular sub-field, covering all the major developments along with the latest breakthroughs. Other secondary sources include books or articles that translate scientific findings for nonscientists or scientists in other fields. Popular science books or articles in Scientific American or science magazines are good examples.

Secondary sources can be a great place to start when you need to understand what’s going on in a particular area of scientific study because they often give readers a big-picture view. Note that textbooks, encyclopedias, and dictionaries are secondary sources as well.

One important complication to consider is that scientific research papers, which are generally considered a primary source, typically present introductory material that provides a reader with important context—general background information, the type of research the authors perform, and a brief summary of what others in the field have already done. So even a “primary” source will typically have parts where it reports on other sources like secondary sources do. Often you can find useful background information in the introductions of papers that are generally considered a primary source.

So when you think “Primary” source, think: Original, new, or first-hand account.

And when you think “Secondary” source, think: reporting on, discussing, analyzing, or summarizing somebody else’s work.

Knowing this important distinction will help you get to the right type of research for your project and will aid you in presenting the best information to your project’s audience or reader.