A primary source is a document of direct experience. It's as close as you can get after the fact to having been there yourself.

Secondary sources, like review articles and monographs, rely on primary sources as evidence.

And tertiary sources, like encyclopedias and indexes, summarize and comment on primary and secondary sources. See examples and how they all interrelate in the diagram below.

How do you tell whether the article you're looking at is primary or secondary? Listed below are examples of primary and secondary journal articles to help you gain understanding of what they look like. Compare the source you've found to these examples.

Primary sources:

• A research study: Detection and Learning of Floral Electric Fields by Honeybees

Secondary sources:

• A news article about a research study: ScienceShot: When Sparks Fly
• A meta-analysis of multiple research studies to compare and contrast their results: A meta-analysis of bees' responses to anthropogenic disturbance
• A review of multiple research studies to highlight the current state of knowledge on a topic: Clarity on Honey Bee Collapse?
• A monograph gathering, reviewing, and commenting on various aspects of a wide-ranging topic: Honey Bee Colony Health

Tertiary sources:

• Wikipedia article on colony collapse disorder.
• Entry on honey bees in the Encyclopedia of Life.